Grainy camera! what an "upgrade" :(

So... Finally got my new MacBook Pro 2020. It was amazing... for about 20 minutes, after which, I made the HUGE mistake of "upgrading" to Big Sur (from Catalina). Before I did that, I went quickly on Zoom and saw the great quality of the camera . Once Big Sur installed, went back on zoom (its my major work tool these days) and was just horrified to see how bad the quality became.

I am not a big specialist of technical stuff and to downgrade back to Catalina is not that easy (tried to follow instructions for that but couldn't do it)

Is there a way to make camera better? or is there a better version of Big Sur out soon?

I just wish I could easily go back to Catalina: was sooo much better !