iMac is frequently extremely slow in loading websites and apps

Have you installed any anti-virus, clean-up, optimizing or VPN software? These apps are not needed on the Mac and will often conflict with the smooth performance of the macOS.

Also, I recommend that you run an EtreCheck evaluation of your Mac. EtreCheck is a safe and recommended utility from a trusted developer and respected ASC contributor. The diagnostic app gathers important info about your hardware and software and reports it back to you. It is very highly regarded and meant to be used with Apple Support Communities to help others help you troubleshoot and resolve your Mac problems. The EtreCheck report will not include any personally identifiable info.

Please navigate to EtreCheck.com and download the free version. Be sure to enable full disk access when you install the app. Once you’ve run the app and created your report please post it with your reply to this message. 

You must upload the full report. To see how, please click >  How to use Add Text when posting… EtreCheck Report.

We can use the EtreCheck report to look for the things that may be causing your problem and advise how to correct them.

The report indicates:

"Low performance - EtreCheck report took an unusually long time to run."

This could be caused by several things, one is a possible failing HD. Your computer uses a Fusion Drive which is made up of a small SSD and a HD fused together with software. The HD may be having troubles. To diagnose it, please download the free version of DriveDX and run the test. If ANY errors appear that means my hunch is correct and the HD is failing.

Also, your computer has 16GB of RAM, is this the original RAM that shipped with the computer or did you (or someone else) upgrade the RAM? If it was upgraded exactly what brand of RAM was used to upgrade it? Most experienced users here only recommend either Crucial.com or macsales.com RAM. I suspect you are outside the USA, if so then I'd recommend Crucial.com RAM as macsales.com is a US company. iMacs are extremely sensitive to using very high quality RAM and many issues caused by RAM is users installing less than high quality RAM. Both macsales.com and crucial.com only sell extremely high quality products at very fair prices and provide excellent support.

You are correct to believe that your Mac should not be doing this.

Your 2019 iMac is likely configured with a 5400 rpm rotational hdd that is often implicated in the poor performance that you describe. That hardware may work fairly well with older macOS versions, but as the OS becomes more complex and demanding the weakness rears its ugly head. The easiest fix for this will be for you to buy an external SSD, install the macOS onto it and use that as your startup drive. The performance difference will be night and day.

The only way for us in the Community to confirm that this is the issue will be for you to upload a fresh EtreCheck report that we can examine. I invite you to do that. There will be no personal data in that report, simply info on the hardware specifics and the software and applications that are installed and might be in conflict or otherwise implicated.

Big clue here:

Performance:

System Load: 0.94 (1 min ago) 1.08 (5 min ago) 1.21 (15 min ago)

Nominal I/O usage: 0.06 MB/s

File system: 17.72 seconds

Write speed: 293 MB/s ⚠️

Read speed: 2272 MB/s

"Write" scores for a healthy Fusion Drive should be 500-1000MB/sec for your iMac model. Try booting into Safe Mode.

How to use safe mode on your Mac - Apple Support

LEt eh computer "soak" in Safe Mode for about two hours, then restart normally and run another EtreCheck test. See if that improves the Write score

Yep, that's the report we were looking for. 🙂

I agree with rkaufmann87. The fusion drive is a potential issue here, as is the RAM if it was installed as an upgrade. Having a deep look at it with DriveDX is a good idea.

I don't see any indication of a software issue or conflict.

I do wonder about a single APFS volume named "Update", but I'm not familiar enough with macOS Ventura to know if that is a concern. That volume does not appear on my Macs running earlier versions. I'm going to assume it's not indicative of trouble. If someone else knows otherwise then I hope they will contribute.

So, run that DriveDX evaluation and let us know what you find.

Well from what I can tell you HD is having issues. My recommendation is to book an appointment at your local Apple Store or Apple Authorized Service Provider (not a Best Buy) and have the computer diagnosed. The HD can be replaced or you can buy an external SSD and use that as your primary drive. You can connect via USB 3 or the preferred method would be Thunderbolt 3. You would need to install Mac OS onto the Thunderbolt 3 drive and then restore from your Time Machine backup to it. Then make the TB3 drive your startup drive.

That option would be less expensive than replacing the HD in the computer and you would likely have better performance than you do now.

A third party Apple Authorized Service Provider could likely do this service for you, an Apple Store will only replace the HD.

Your iMac is still supported hardware, so Apple could service it and perhaps replace the failing drive. I've no idea what the cost would be and assume that it is no longer eligible for AppleCare.

If you would like to make a Genius Bar appointment for hardware service and support use this link – Contact Apple for support and service - Apple Support

An option would be to employ an eternal SSD as your startup drive. The computer is not old enough to be given up on, imho. It's fairly easy to get ten years of use from a Mac computer.

As for using it as a monitor for an M2 Mac mini, that's a non-starter. It cannot be used in that manner. It's a computer, not a monitor. There are third-party options, but none that would likely be acceptable. If you buy a mini, also buy a monitor for it.

I appreciate that you tried to get that report posted, but it just didn't work out. What I see here is incomplete and of little help.

Please navigate to EtreCheck.com and download the free version. Be sure to enable full disk access when you install the app. Once you’ve run the app and created your report please post it with your reply to this message. 

You must upload the full report. To see how, please click >  How to use Add Text when posting… EtreCheck Report.

No report is attached. Please save the report to your Desktop and then follow the directions below to post it:

For instructions on how to download your EtreCheck report and attach it to your reply to this message please click https://discussions.apple.com/docs/DOC-250000211 It is helpful to us if you download the report to your Desktop.

What I would recommend is the following:

https://eshop.macsales.com/shop/envoy-express/thunderbolt-3

It is more expensive however it offers 4TB of storage and is the fastest SSD out there. Also, the vendor (macsales.com) only specializes in Macs and they are very knowledgeable, offer great service and are used by many experienced users.

Personally I am not a fan of LaCie drives because they ones I have purchased failed prematurely. However that being said there are many that like them.

I would search for an independent Apple Authorized Service Provider in your area that will do this upgrade for you. As I mentioned earlier an Apple Store will not do this. PLEASE, do NOT use a shop the services PCs. Find someone that can tell you they are an Apple Authorized Service Provider, why...simple they have been trained by Apple, have the proper tools and should know what they are doing. General PC shops may have some experience, however they do not have the training or tools.

It is not difficult if you are used to working a little with computers.

1. Format the new SSD as APFS in Disk Utility
2. Then install Mac OS onto the SSD, you can do that from the recovery Partition. (Restart the Mac and hold down Command + R on startup)
3. After Mac OS has been installed on the SSD then set the SSD as your Start Up drive in System Settings.
4. Restart the Mac and verify it started from the SSD.
5. Run Migration Assistant and migrate to the SSD.

Please post the EtreCheck report and someone will review it with you.