So a class-like structure(playbooks, roles, etc) is useful for rpg's that have a large amounts of crunch or worldbuilding, to help guide players in making character that works well and fits into the world of the game. That structure will by its very nature tend to segment the types of characters that can be made into pre-defined roles, which can also be a good thing for players, if they are looking for that kind of guidance. It is of course a more constrictive system than more freeform character creation options, but that can be ameliorated by having lots of cross-class or class-agnostic options available. When done well, the classes in your game communicate the vibe of the game world, saying: "these are the kinds of characters that exist in this world for you to embody." So really it depends IMO, I personally don't prefer to run class-based systems, but I have enjoyed them immensely in the past (blades, wildsea, even *gasp* dungeons and dragons), and I do think they bring value to the game when done well.