Steam should not allow mandatory third party logins whatsoever.
optional ones, fine, but as soon as game modes or even whole games are locked behind a third party login it shouldn't be allowed on Steam
Don't really care, if a game uses a different launcher I just buy the game there, it never made sense to me to get it on steam if it's just gonna load up the other launcher and it's relevant overlays anyway; after pressing play they launch the game just fine, which is all they need to do