I think the OP is objectively correct about it not making sense to buy games at launch. However, once in a while I do it anyway, because I am excited about a game and want to play it as soon as possible, or because my schedule will allow for more gaming time at that point. But, I probably only do that for 10% or so of the games that I buy.
However, as I've been subscribed to game pass for several years now, I often do not wait for games that are launching on there. If I'm interested in them, typically I will play them at or very close to launch. My subscription includes them, so there's no real financial risk involved in trying out the games early.