The rest of the stuff you cited does sound dumb, but in many RPG circles, "walking simulator" simply refers to the type of game where you spend most of your game time literally walking around in 1st/3rd person in some big/open world to get from place-to-place, and with nothing all that exciting happening very often. Maybe you don't like the phrase, but it's a decently safe bet that Starfield will be one - Bethesda doesn't really make anything else.
So you don't know what a walking simulator is either.
So called "walking simulators" was specifically coined to refer to games like Gone Home and What Remains of Edith Finch, games that have minimal interaction and that tell their story with their environments rather than NPCs or cutscenes. Walking around their environments is literally how you get the game to unfold.
What it isn't is any game that you find boring. No Bethesda game is a walking simulator.