How would playing in FR automatically make you the plaything of a far more powerful NPC? It is not feasible for the chosen to meddle in every problem out there (they simply don't have the time)? I am fairly sure there would be a small corner of the world where they can carve out their own niche.
Not having much of a horse in this race, I'm still going to play devil's advocate here. If you offered that argument to my players, they'd be even
more inclined to skip out on the game, not less.
It's the damning with faint praise effect. Every time someone says "the Chosen don't have the time to deal with the problems you would," it carries the implication of "because they're doing more interesting and important work." When you say the PCs might get "a small corner of the world," that implies that everything else is for the NPCs.
Now, I'm probably misreading your emoticon there, and you might be parodying this very effect (if so, I apologize). But this isn't the first time I've seen the argument that players should be perfectly happy in the Forgotten Realms, if they just realize that the NPCs more powerful than they are too busy doing cool stuff and shaping the fate of the world to involve themselves in the (strongly implied) pettier adventures that are more the PCs' speed. It's just not a selling point. It comes across as the idea that players should be grateful for crumbs from the table.
If you want to sell the FR, I'd think it would be more effective to say "Yeah, theoretically these NPCs should be the stars. But they're not. You're going to surpass them. When they come to you for help, they're going to be grateful for it, because you're saving their bacon. Want to find out how?" It's a useful tool, having NPCs as a benchmark to measure the PCs against. But if you want to really get the players' attention, it should be clear that said measurement will end up being flattering to the PCs.
I think that any game setting winds up having different needs depending on whether it's being actively gamed. Having Drizzt be the star of a grand show is great for selling the setting as something to explore. Having the player characters doing things
more interesting than Drizzt is what makes a setting gameable.