In general, the game's tutorial seems to be missing a lot of information, but something that I haven't seen anyone mention yet is that there is no way to know what a class's progression looks like while within the game.

I've played enough 5e to know more or less what each character can do, but there are a non trivial amount of changes to several classes, and spending several hours of game time to find out that a build is not viable is a bit of a kick in the teeth. It's also useful to know ahead of time what feats are available so that you can plan your stats and subclasses accordingly.