We're sorry to hear about the slow performance with Lightroom classic. Since when have you been seeing this issue? Have you tried any troubleshooting steps so far?
Please try turning off the use of Graphics Processor option from Lightroom classic preferences. Go to Lightroom Classic > Preferences > Performance tab > Uncheck "Use Graphics Processor" > Restart Lightroom Classic & check if that helps.
Try Onyx (it’s free) to rule out a corrupt cache or application state, instructions below (I was a Mac IT pro for 25 years). I've fixed app issues thousands of times with it! Download the free Onyx (https://www.titanium-software.fr/en/onyx.html), select the Onyx version FOR YOUR MAC OS, download, run it, reboot.
In Onyx run almost everything in the Maintenance tab, deselecting things you may not want deleted, like Launch Services. Hit the "Options" button across from "Internet" and check/deselect more stuff like Cookies & Other Site Data, Browser History, Form Values, (which are OFF by default), but make any other choices you want to keep. Don’t know what something is? Google it, or ask me, or don’t run it, then hit Run Tasks. After it's done it will ask for a reboot. You will see you've gained some hard drive space.