I have never needed to reboot because of permissions, basically just had to click “allow” a few times, so this stuff doesn’t really bother me. It’s a very slight inconvenience.
Big Sur performance on older hardware has been a disaster though. Even on a $2500 MBP 15” from 2017. On M1 though it’s excellent.
If you're referring to the Kext/DriverKit changeover, this is just false - Kexts still work in Big Sur, they're just trying to slowly shift the ecosystem to DriverKit. Nothing has truly changed there yet.
If you're referring to a broken thing within Kexts/IOKit itself, that would be a pretty severe bug that would get attention within Apple. I feel confident saying this as I've reported bugs like this and they get appropriate priority levels.
Lastly, if you're writing (signed) driver code, you generally have access to resources within Apple to get answers to questions. I'm not even a large company and it was relatively easy to get in touch with those teams - and this stands in contrast to other teams within Apple.
Big Sur performance on older hardware has been a disaster though. Even on a $2500 MBP 15” from 2017. On M1 though it’s excellent.