This is the "appeal to tradition" fallacy. That something "has always been such-and-such" is not a compelling reason why that state of affairs should continue.I too agree with bringing back class/race restrictions. For one it perserves the archtypes, and D&D has always been a game based around classical archtypes.
You speak of flavor. Isn't a character that breaks the mold much more flavorful than someone whose following in his race's pre-ordained footsteps? A player character is, by his very nature, exceptional. He can be the rare, almost-unheeard-of halfiing wizard.IMO, leads to more background flavor for the races themselves...its why hobbits/halflings are so enamored with magic, because they cant be wizards themselves, etc.