It may be time to replace my 2019 iMac with Intel. Any suggestions?

Before you obtain a new Mac, I would follow the advice provided already by others here:

(1) make sure you have 20% free disk space, you have less than 10%

(2) run Etrecheck and post the output here, there may be something obvious to adjust that will make your Mac fast again.

We are still using two 2019 era MacBook Pros, Intel, not the same Mac as yours but from the same era and they are quite snappy still. One is used for intensive Photoshop and Lightroom photography image processing and it runs well but does slow down when free disk space is below about 10%.

The question posed earlier about what type of internal drive you have is very relevant, because the Mac pages to disk frequently and when you are low on disk space that can slow things to a crawl, especially with a mechanical drive or fusion drive.

The other thing you need to address (maybe a separate more focused question here would be good) is why files are going missing. That is likely due to some sort of misconfiguration having to do with your combination of external local drive storage of photos plus iCloud photos plus ... that situation needs to be addressed, because when you get a new Mac it will likely be "migrated" over and persist even with the new Mac.

I see from your list:

Photos 241.48 GB on removable disk

iCloud Photos 104 GB

Music 75.54 GB on disk

Music Media folder 19.49 GB on disk

Documents moved over to iCloud 147.93 GB on disk

iCloud Drive 830.01 GB on disk

"Photos, music, Contacts, and documents come up missing."

Your Music is stored multiple places?

iCloud Drive has 830 GB "on disk" does that mean it is also locally stored or is it both in iCloud and on your Mac? I don't see 830 GB of files from your list in iCloud. Is your Music in iCloud also? When files in the Documents folder are "missing" when iCloud is in use, those files are often found in iCloud, for instance in iCloud Drive.

What does Documents moved over to iCloud mean? Does that mean they are physically moved to iCloud and no longer on your Mac?

Contacts missing is mysterious, usually people sync their contacts across multiple devices by using iCloud for Contacts.

Do you have multiple devices? If so, you need to check that each one is logged in to the same Apple ID and that you have consistently configured them to use iCloud consistently. For instance, if one device is not using iCloud for Photos and Contacts, its Photos and Contacts won't match up with the devices that are. There are many details like these that you haven't provided information on.

Here's what I do:

• Photos - all in iCloud. All identical on multiple Macs and iPhones set up the same way as such.
• Contacts - all in iCloud. All identical on multiple Macs and iPhones set up the same way as such.
• Music -- I don't use Apple Music, but purchased music shows up on all devices as they are all signed in the the Apple ID used to purchase music from Apple.
• I don't use iCloud Drive. I do use Dropbox, which is similar, and I have all those files both in Dropbox in the cloud as well as locally stored, they mirror each other. On all the Macs. On the iPhones most of those Dropbox files are only in the cloud.
• Messages -- all in iCloud. All identical on multiple Macs and iPhones set up the same way as such.
• Multiple Time Machine backup drives in use for each Mac. I use more than one (two or even three) so a Time Machine disk failure won't impact me. At least one "clone" backup for each Mac using SuperDuper.

I think things "coming up missing" may be due to some inconsistency between how files are being stored (a) in iCloud, (b) in your Mac's internal drive, and (c) on your external drive. It would be good to sort this out before moving to a new Mac so you don't just bring those issues over. I think this may be a different problem than the slowness, which may have a more straightforward solution as suggested by others.

If you really want a new Mac then I'd suggest getting a Mac mini, for your needs for less than $1500 you can buy a nicely configured MM and a Samsung display and have a machine that far outperforms your iMac. To migrate, it is very simple if you just follow the directions below:

·       Always connect your old Mac's Time Machine External Hard Disk prior to startup, this will allow a migration from your TM backup and it will be dead simple! When you start the new Mac for the first time it will startup Setup Assistant (SA), SA will get to a point where it asks if you are migrating from another computer, select Yes and follow the on-screen prompts and it's done! It is that simple! This is the easiest, quickest and most reliable method to migrate from the old Mac to the new Mac is to simply connect the old Mac's Time Machine External Hard Disk to the new Mac using a USB cable before you turn on the new Mac. 

·       NOTE 1: You will likely need a USB A to USB C adapter, you can find them on Amazon for $10 or less.

·       NOTE 2: If you have already done SA on the new computer then simply connect the Time Machine External Hard Disk using a USB cable and launch Migration Assistant (MA) which is located in Applications - Utilities - MA. Then follow the on-screen prompts.

·       The ONLY difference between MA and SA is MA will create a new user account that you need to log into.

Both SA and MA migrate applications (not 32 bit apps), data files & settings. They do not migrate Mac OS itself. Some professional apps such as Adobe and Microsoft apps may require re-installing their apps as they will not allow them to be migrated. As long as you kept the security keys for installing their apps, it is not an issue. 

Finally, never EVER use Wi-Fi when doing Setup Assistant or Migration Assistant. Why, it simply fails in most cases. Please read and follow the directions in Setup Assistant and Migration Assistant. If you do not have a Time Machine backup of the older Mac then create one! If you are not aware of Time Machine, please read Back up your Mac with Time Machine and finally if you need an External Hard Disk to use as a Time Machine External Hard Disk then many experience users on these forums prefer the OWC Mercury Elite Pro due to it's reasonable price, high level of quality and ease of use. 

However, I suspect there is a lot of life left in your current machine but there may be some issues that is causing poor performance. In order for us to tell though we need a report, please read below.

It will help us get a good idea of what is causing your problem if you provide a report of your system, that way we do not have to play 20 questions with you. The report we are requesting does NOT provide any personal information and is extremely safe to use. Please navigate towww.Etrecheck.com and download the free version of EtreCheck. Once you have you downloaded the app and installed it, please run the report and save it. This report will help us get a good idea what has been installed on your system and help us be able to diagnose what may be wrong.

When you have your report, you can attach it when you reply to this message and we can then review it and help you determine what is needed to get your system running well again. 

For instructions on how to download your EtreCheck report and attach it to your reply to this message please click How to use the Add Text Feature When Post… - Apple Community It is helpful to us if you download the report to your Desktop.

You don't need a new Mac you need to determine what's causing your current Mac to perform way below expectations. Download and run Etrecheck from this link.

Copy the report as shown below

and use the Additional Text button to paste the report in your reply.

Then we can examine the report and see if we can determine the cause of the problem.

Your iMac Retina 5K , 27-inch, 2019, 3 GHz i5 w/ 32GB RAM is a good machine. It should be running as such.

The main problem is that your drive (probably a Fusion drive) is way too full - 92% full based on your info.

"Macintosh HD Used: 958.93 GB on disk Available 72.44 GB "

There may be more issues, but the full drive is the #1 problem to address. I suggest for starters that you find a way to remove at least 250GB from your drive. You should notice a distinct improvement in performance.

That said, it would also be helpful if you download & run Etrecheck and post a copy of the results here. It is a diagnostic program, does not reveal any personal information.

Do you have a 1TB SSD or a 1TB Fusion drive?

If you have a fusion drive getting a 2TB external USB-C SSD and reinstalling MacOS onto that for use as your boot drive may solve all your performance issues.

Use an external storage device as a Mac startup disk - Apple Support

Second to clearing stuff off the internal drive, you could consider installing macOS on an external SSD like this one and running your Mac from it. It's a lot less costly than buying a new Mac.

If you like your iMac it has a 5K display so any display less than that you may not like. I replaced mine with a Mac mini and a 5k display (LG less cost than the Apple display). You could also try using an external drive (TB would be fastest) which will improve the speed much greater at a lower cost if you have a fusion internal drive now.