My Geek Life

I would agree if there was no such thing as multiclassing. As long as multiclassing remains viable and all classes remain tied to ability scores (or just one or two, as the case may be), there's still some relevance to ability scores. You're right, you may not want to support the dumb wizard or the weak fighter, but you might want some mechanism in there to keep the wizard from also being the fighter. Or not, you know. I think you're pretty much right as far as primary ability scores goes, but where they make more sense is secondary ability scores. Sure, my fighter is probably going to be brawny, but is he also smart? Or is he charismatic? That's going to affect skill choice, for one thing, which is pretty relevant.