Ok, that's some BS. Clerics, Wizards, Druids, Sorcerers, Bards and probably a bunch of other prestige classes could absolutely use meta-magic feats in 3.0, 3.5 and the eventual 3.25 which blends 3.0 and 3.5. The group just decides in the beginning if they will use the stronger or weaker rules, and plays 3.25 with that set of rules, though pretty much everyone goes with the weaker set of rules for druids, because they were OP in 3.0 and while they buffed all the martial classes for 3.5 so they could keep up with the other magical classes, they nerfed every magical class except druids, which they made even more OP.

The real decision is if you're going to use the stronger or weaker rules for the magical classes, except druids. For martial classes, use the stronger rules. For druids use the weaker rules. For the rest of the magic classes, use the stronger rules if you want to become gods, use the weaker rules if you only want to become an epic level party.