If Apple still made great software and even better hardware then I wouldn't care, but that hasn't been the case for years.
Reasons to stick with them: company purchasing policy.
...for now.
and kexts [will] have a userspace alternate.
...which is unlikely to have the same performance and control benefits as running "on the hardware", and I bet they will also gradually lobotomise the APIs in userspace too.
Apple's control-freak attitude is nothing new. This is just another step along their plan to turn desktops and laptops into the same dumbed-down walled-garden platform as mobile devices.
I suspect that even Linux will be adopting a more restrictive (if decentralized and overridable) model for third party binaries sooner than later.
because it’s become increasingly clear that unquestionably running code that can steal or destroy user data and especially code with kernel access is a catastrophically bad idea in an always-connected world
...and over the years I have increasingly become convinced that "security" is simply a convenient and difficult-to-oppose excuse to take away freedoms and push society towards an authoritarian dystopia by spreading such fearmongering paranoia. There's enough sci-fi around to show what that could look like.
... and presumably you'll continue to feel that way right up to the point that a bit of malware steals your banking credentials or encrypts your hard drive and demands a Bitcoin ransom.
You absolutely do not need kexts to steal user data, it's totally orthogonal to user's data security, and I think (correct me if I'm wrong) even in Catalina this XKCD is still relevant: https://xkcd.com/1200/
Can you tell what is a better hardware and/or software for you?
Did you had any 32-bit software that don't exist as 64-bit versions?
I have at least a dozen off the top of my head. Probably more if I actually checked (which is why I'm not upgrading)