iMac running very slow

Your biggest problem is the 5400rpm mechanical hard disk drive that is your startup drive.

The read and write speeds are lower than optimal and can't keep up with the demands of your OS and applications, especially the Adobe Creative Cloud apps. I suspect your iMac was never a speed demon and your recent upgrade to Big Sur has probably amplified the issue.

I would suggest you purchase a SSD (Solid State Drive - no moving parts - MUCH faster than the HDD) and use that as your boot disk. You can replace the internal HDD with the SSD, or for simplicity, get an SSD in an external enclosure and connect it to your iMac's Thunderbolt or USB port. You'd see an immediate and surprising improvement in speed either way.

You can research SSD options here:

click > https://macsales.com

Otherwise, I think you EtreCheck report looks pretty clean.

We cannot help without information. At minumum, we need your iMac sub-model (including screen size) and current OS version. Those are quickly available by doing "About this Mac..." from your Apple menu like this:

We also need to know what is slow. Start-up? opening apps? Executing tasks within an app?

We can neither see nor touch your computer and must rely on you for 100 percent of the details regarding your Mac issues.

From Apple's help document on posting questions here:

Hi mokette,

Welcome to Apple Support Communities!

The reason your iMac is very slow is due to the 5400 rpm hard drive. Very slow. If you use an external SSD and run macOS from that, it will make your Mac 10 to 80 times faster for storage, depending on what external SSD you buy. For more info, instructions, and what external SSD to buy, please read: How to Setup and Use an External SSD as y… - Apple Community.

-Jack

I got three answers to my question -- all the same so I took everyone's advice and got a separate SSD and thunderbolt cable. I followed Apple's instructions for making it all work and they were WONDERFUL! So clear and step-by-step. Thank you Jack and the others who helped me fix my S L O W computer. Cheers!

I believe we need to proceed with an EtreCheck report. EtreCheck is a useful App to diagnose and identify issues, both hardware and software. It is trusted by many users. Please follow the steps outlined below:

1. Navigate to: https://etrecheck.com and get the free version of EtreCheckPro.
2. Download it. It is a free and trusted app. It is often recommended here on Apple Support Communities. 
3. Open EtreCheck, and before running the report, be sure to check “Allow full Drive Access” at the bottom of the EtreCheckPro window.
4. Run the report, and put it in a post, as seen here: https://discussions.apple.com/docs/DOC-250000211. We will then examine the report for issues in your Mac.

Cheers,

Jack

Do you still need help? We haven't heard from you in a while.

Cheers,

Jack

👏🏽👏🏽

🙂