It's the mandatory changing nature of the game that bothers me about DnD.
In other games I'll set a power level and the campaign will stick to that, allowing us to have a consistant story.
In DnD it changes the longer you play, you have no choice about the game 4 months later being radically different in scope and nature from the game today. You have to tell a different kind of story then than you do now, and on the other end of the table you have to play a 'different character' then than now (even if the same person).
A change in scope and nature is fine if driven by the developing story, but in DnD it's driven by a external unescapable mandatory artificial mechanic.