[2023] Haven't played since 2016, what major changes have there been?

Honestly depends who you ask. There are some who will tell you that literally nothing has changed in the last 10 years; And there are also some who will tell you that every single major patch has changed EVERYTHING in the game so dramatically that every new patch is basically a whole new game.

You'd honestly be best off just hopping in to play and see how it goes.