Ask a D&D player to make a character, and explain to them that they will never increase in level. What level character will they make? If your D&D game has become all about leveling-up, why not put an end to it. Run the game with the characters they want to play. I designed one game that has no real XP system. Characters can be tweaked, but they do not increase in power.
And we liked it!
Get to the roleplaying, get to the world saving, and get to what most GMs want most of all, engagement.