d20 sucks. Classes are really stupid. Theres only this that and the other class. Well what if I want to play a sex-slave or something like that? 'Oh well you cant be that, you'd probly have to be a thief/scoundrel/whatever' And there theirs the prestige classes where you have to get so many class levels before you get to be able to choose an advanced class... "What theres no Head-harem Girl?" lol d20 is dated, even with revisions, it needs to be retired.
I agree with everything that the originator of this post mentioned. While Im not a big fan of GURPS (it in itself is a bit clunky), but it is definitely a big improvement over d20.
And no, d20 wasnt made to be made to be easily reworked... have you looked at the millions of tables they have in those books? They have to have several different books, all of them near-dictionary size in thickness just to contain all the rules... where-as GURPS, WoD, and a couple others only have ONE book for the actual rules, everything else is setting supplements.
I think if youre gonna do a fantasy setting, or a scifi setting, the game engine for Exalted (white-wolf studios) is one of the best.