I think 4e D&D rewards skilful, intelligent players at all tiers of play, in a least two ways: skill and intelligence are needed to achieve the benefits of cooperation and synergies in combat situations; and skill and intelligence (and also imagination) are needed to fully engage with the fiction (via p 42 as the resolution guidelines), both in and out of combat.
Here's an example of the latter, from upper Epic tier:
This is the sort of thing that of course will play differently at different tables, But because 4e has a consistent, coherent framework for establishing costs (action economy, recovery or non-recovery of abilities within a common resource suite, sacrificing permanent items (or item-equivalent effects), etc) and DCs (the DC by level table); and because the fiction of tiers is pretty clear and other parts of the game (like Paragon Paths and Epic Destinies) reinforce that fiction, meaning that appropriate effects are also reasonably identifiable; the game facilitates rather than impedes a particular table reaching a consensus about how something like sealing the Abyss can, mechanically, be done.
One thing I like about them is that they are express ("in your face"). The PC is a demigod, or one of the Raven Queen's chief marshals, or - in the case of the chaos sorcerer PC in my play excerpt - an Emergent Primordial.
An emergent primordial can do more than just hang out at the tavern waiting for quests. They're the sort of being that might seal the Abyss!