I have a iMac Retina4K from the end of 2015 with 3.1GHz Quad-Core i5 and 8GB DDR3 on 21" with a second monitor attached, and a HDD-disk. macOS is Catalina and I am running Firefox, Adobe InDesign and Adobe Illustrator most of the time. Since I upgraded to Catalina my Mac is soooo slow that starting up in the morning until anything really runs (i.e. I am able to click on an app) takes up to 10 minutes with no applications opened yet.
Opening up Illustrator works in 6 of 10 times, else it just freezes. If opened it does work okay though. Firefox freezes also on a regular basis. I never open up more then 3 applications at the same time, have no widget etc running and I got hundreds of gigabyte diskspace left.
I get it, that this isn't the newest device but shouldn't the OS and some really simple task like opening up a browser be "there" in less then 5 minutes?
My question though is a different one: If I'd set up/reinstall the Mac completely new with Catalina (as I am bound by Creative Cloud to it) should that speed up my described routine or is the current scenario just what I can expect from the combination of that hardware/software combination?