>But I have never, and probably will never, buy game from anywhere that requires me to install a launcher and look at advertising before I get to play.
You'll be happy to hear that Steam does not require you to do any of that. If the game does not heavily rely on Steam services you don't have to have Steam started at all. I just tested some games and i could just start them from the executable without Steam running. I also disabled the news window you can get on startup and the Steam client starts on the library, not the store page.
So have fun.