Many classes do not get any choices at many levels. Sometimes the choices are thin.

True. But I’m also playing with Xanathar’s and Tasha’s, and with a choice of so many classes, you tend to gravitate towards the more interesting ones, so if one class is a dud, it doesn’t weigh too heavily on the game when there are more interesting choices available.

Also class-and-level is only one way to make a game. You could just not do that and open up whole new worlds.

You can, but it’s not an inherent downside to have classes like this either. The things they’re allowed to do and not allowed to do create some clear strengths and weaknesses.