Although some of the ones I'll mention could be subsumed under the "it isn't realistic" banner, they get enough individual attention to rate mentioning on their own:
* hit points don't make sense!
* levels don't make sense!
* the next edition of D&D needs to do away with all the sacred cows!
My answer for all of these is the same, and is simple: Play another game. It would be like me demanding that Pendragon stop focusing on knights or get rid of the Traits and Passions, or inisisting that Ars Magica needs to be more low-magic. There are plenty of other RPGs that fit the bill of what you're looking for.
Other arguments that I'd like to see go away:
* this game is better than that one! Whether it's old schoolers lamenting d20, or everyone else lambasting HackMaster, it's a futile argument - it's all subjective. If you don't like something, then don't play it. Loudly proclaiming how one would like to see this or that game "go away" is stupid. Just because I don't like something doesn't mean it has to be destroyed, or that anyone who likes it is stupid or deficient.
* Too many options in 3e! Huh? It is easy enough for a DM to limit what goes in his game from even the core rules. Why do away with options that others like because one can't control one's game?
* Mercurial swords - while it hasn't been discussed lately, I'm still surprised by how much consternation this subject caused.