Yes, our situation is very similar. We also come from the DOS era so it was clear to us that co-op in BG3 would be just like that. Give me one damn reason why it shouldn't be like that!
I never thought it would be the way it is but it is what it is.
We had very outdated tech in our household, a PS4 and a 32'' TV. BG3 was the main reason to upgrade our tech. We bought a PS5, a second controller and a new TV. I initially wanted a 48'' TV because I'm not a fan of really big ones but in the end, we went for 55'' since that seems to be the new standard. Luckily, we opted for the larger TV!
I can't imagine playing this game in couch co-op on a smaller TV without rearranging the living room. I know from many games that it's usually safe to wait another six months to a year until the game runs as it should. Well, in the future I won't be preordering games from Larian anymore and if there's a DOS3 or something similar, I'll wait and see first.

What is gradually but undeniably incensing me is the fact that the game has been out for a while and there is no communication regarding future update plans or how priorities are being addressed. that sucks!