Easy way to find out is to turn off auto-downloads in your client and then connect to a server. If you don’t have some file that the server requires you just get dropped back to the main menu so you can try somewhere else.
Or you can just play on non-pure servers. Then you don’t need to be in perfect sync with the server to play.
For the most part, this is a problem with the way admins set up their servers and not something wrong with the game design. So you’re probably better off whining at specific server admins and not at the game designers. Naturally, its a safe bet you won’t make too much traction either way. =)
RK