Firstly, that I think light oneshots and crunch or narrative heavy longer campaigns have a substantial qualitative difference.

True. I'm really not sure how someone could get introduced to them, though.

I used to agree WRT D&D being a good game to introduce things, but I'm increasingly opposed, for a couple of reasons.

Your reasons do make sense. My main problem is that I'm not actually familiar (in practice) with much fantasy roleplaying other than D&D. If I'd played it, I'd probably suggest that new players start with Dungeon World – but I'm a bit limited in only having read about it.