You have a point. The downside of using non-custodial platform for a newbie was it has a lot of limitation such as limited amount of fiat you can exchange, limited to ETH token and some exhibit a more complicated user experience unlike custodial wallet that was easy to use, Just sign up and verify then ready to go with a high deposit limit plus you are free to trade on any pair that you like.
Yeah, it's really very difficult for most users, confusing and in fact, has very little in the way of giving a newbie reassurance (which is what centralized exchanges are really good at doing haha).
Like you said, most CEXs give you the whole sky after you verify.