So for Company of Heroes 3 units that I never see people using... Mind you, that's not exactly from the largest sample size since I don't spend a ton of time watching a game that I find to be extraordinarily boring.
Interesting. I honestly see most of the units you've mentioned pretty regularly, with the exception of Footguards and the Wehr Flak 30 AA Team... It just sounds a lot like you just don't really play the game to be honest. All of the other stuff you mention is probably down to personal taste, I think there's quite a bit of room for build variety, especially when you consider the extremely limited number of battlegroups that are available currently.
I do share your concerns on the number of global upgrades though and a certain 'lack of feel'. It's difficult to describe, almost as if units feel a little bit weightless, for want of a better term. I guess because it uses a different engine?