A lot of people believe that high level D&D is bad because they try to make high level gameplay on middle of Sword Coast... Wanna a high level(14+) adventure? Go for frozenfar, underdark, in a elemental plane, in far realm, feyworld, or something similar.

Most TTRPG adaptations that goes for high level have you spending a lot of time in this regions. nwn1 Hotu after a short introduction has you going to the underdark and then to the 8th layer of hell. nwn2 MotB you even visit the wall of faithless. BG2 campaign end by you facing your arch enemy in HELL. On ToB you gain a hellish pocket dimension in literally the second place that you visit. And most of conflict on the "material plane" is caused by other Bhaalspawn, Pathfinder Kingmaker has you visiting and dealing with creatures from feyworld a lot.