There are Bethesda games as in made by the studio and Bethesda games as in the game genre that only Bethesda (And Oblivion once) produces with their proprietary game engine. A major aspect of the game genre version of Bethesda game is that the "main" story is neither necessary or important for the player's enjoyment. The main story is typically one of many things the player can do and is not usually what fans of the genre are most interested in. Finishing a Bethesda game means doing everything that's in it or getting bored at some point before that.

There are still tons of people playing all Bethesda games from Morrowind to Fallout 4 to this day with active mod scenes and setting discussion communities keeping the playerbases of those games alive. People having a nice enough time after the story and quitting since there's nothing else interesting to do is not what fans of Bethesda games want from a game like this. Compared to other linear shooters I'm sure it's fine enough, but I don't think this is what anyone wanted for Starfield.