Perhaps an alternate approach:
If most people never make it to level 12+ in a given game, and even when they do it takes multiple years to get there...
Why not chunk the game into three separate 10-level brackets? You'd cut down enormously the amount of cognitive load new players need to take on in order to learn, create massively more space to include more options without overloading the core books, and be able to focus really hard on making those first 10 levels the best they can possibly be. Include options for how to spool out the fun even once folks are level 10, so they can get that feeling of the final level or two (perhaps with some "powerful boons" that are equivalent to being a level 11-12 character) without actually needing such levels printed.
Then, a year or two later, add Paragon tier, 10 more levels to play with, with an emphasis on grander, more fantastical, more high-octane stories. And, finally, a year or two after that, add Epic tier. Without needing separate chapters on races, and being able to just extend out the class feature tables for classes, each book should have plenty of room for its own new bits and bobs, while still permitting a relatively streamlined structure.
That way, not only are you focusing on only the stuff people can realistically use early on, you're keeping things light and simple, and giving direct support for those folks who prefer a low-magic experience. And with all that extra page space, you can have actual "novice level"/"zero level" rules baked right into the PHB, so players can see them and be able to use them if they want a more tailored introductory experience.
I hadn't really thought about doing things this way before, but the more I think about it, the better it sounds. Especially because you can attempt to fix the "Fighters just fall short" problem in P/E tier with various beyond-the-mundane additions (a la 4e's Paragon Paths and Epic Destinies.)