I've been playing D&D on and off since 1982, and I've played/DM'd basic, 1E & 2E AD&D, 3E-5E D&D and now the revised 2024 version. In all those years I don't think I've played a character or DM'd a campaign that went past level 10. I think I'm being a bit generous with that number too, and most games probably ended by level 7 or 8 for whatever various reasons, TPKs, groups broke up, etc. For me this is one of two things, 1) Just remove levels 11-20 from the core rules and address it for those who want it in a future book, or 2) expand the core rules to more than the traditional 3, PHB, DMG, & MM, to add a book of optional rules or two. I don't think it's as easy as just saying keep those levels or remove them, but if it were up to me, I'd get rid of them.