Okay, that’s strange. When you say workstations, I assume that you had pretty decent hardware and probably more powerful than my consumer notebook. I usually don’t notice lags or load times > 1 second. If I do a complex operation like mass-cloning an object via a polar pattern, I have to wait for 2 or 3 seconds but really nothing that bothered me in the workflow. Definitely never anything close to a minute as you described.
If you want to give FreeCAD another chance one day and still experience the same issues, maybe bring it up in the official forums. The experts there might have an idea what could be wrong.
I run Firefox with uBlock Origin in my work as well as private device for > 2 years without any issues including tricky applications like Citrix, Virtual Desktops etc.
On my mobile, I use Fennec with uBlock Origin, Decentraleyes and PrivacyBadger and sometimes have some small issues, so I have to view the page in Desktop mode instead.
But compared to a web full of ads, it’s a difference like day and night. Definitely won’t go back any time soon!