iMac slowed down massive after small Update to 10.15.7

Thank you for posting the EtreCheck file. That is a big help. Someone else may have some further suggestions to offer, but here are my comments.You have only 12GB of RAM installed and you are running Catalina, which should have a minimum of 16 GB RAM. I would upgrade your RAM to 32 GB since you appear to use a number of RAM intensive apps. It is important to only get RAM from a reliable source. We recommend crucial.com or mac sales.com. Otherwise it often does not work. You also have an internal slower mechanical hard drive which is slower than an SSD. Additionally, there are some things you can do which will help. I hope the following is helpful to you in dealing with a slow computer. Often times there is a specific cause for slowness and other times any of the following actions may be helpful. They are “maintenance” steps which are often ignored by many people.

·      It is important to occasionally restart a Mac. Ideally, once a week or more often. This does some system cleaning.

·      Regularly clearing the history of your browsers can help as all the data is stored in RAM. Clearing frees up RAM for system use.

·      Some people seldom empty their trash. If you haven’t, then do so. Also empty your email trash.

·      Some programs use a lot of RAM. (Like many Adobe apps and games.) When using them, close any other apps not being used. This step is important.

·      Doing a restart in the Safe Mode can clear a number of problems. This is done by holding down the Shift key at start up. This process can take up to ten minutes while the computer is doing its maintenance and cleans the cache. You may then restart normally.

·      It is also a good idea to periodically run the Disk Utility app. If it reports some issues, then rerun it repeatedly as needed until the final report is ok.

·      On some computers such as yours the problem is simply that there is not enough RAM installed for RAM hungry programs that are being used. fortunately, you can upgrade your RAM. Be sure to order it is module sets.

I hope these suggestions are helpful and enable you to speed up your computer somewhat.

As I understand it, often times when a new operating system is installed, there is internal work that must be completed and this often takes a day or so to complete. During that time the Mac will be slower, but this is a temporary situation. So, your situation was not all that unusual.

You can certainly try reinstalling the OS. I'm not sure it will change anything, but it's worth a try. The other possibility is that your drive may be starting to fail.