Clearly he has no idea how much ancient software remains in use because people have no interest in upgrading. My dentist uses some software to manage her practice - keeps patient records and x-rays and such. It runs in Windows XP. She runs it on a newer Mac in Parallels.

If I bought a new Mac today I wouldn’t buy an M1. Too much old Unix software hasn’t been ported yet. I’d find one of the leftover Intels that are still available.

My Macs run the older MacOS release. Corps run RHEL for a reason. The list goes on and on. No, you don’t have to upgrade anything.