I think it's fair to want a world that changes based on your imagination or on 'the fiction' rather than in response to the PCs leveling, or within the limits imposed by a set of guidelines. Guidelines that you 'need' to follow if you want certain aspects of the game to 'work' - like class balance or encounter difficulty, that is. If you don't care if those things work, obviously, you're free to ignore the guidelines and run how you like - your players can deal with the consequences, figuring out which classes to play and what challenges to take on as they develop 'player skill' appropriate to your style.