I don't think that the fix is making the endgame harder to reach.
But rather, making the level itself less important. Levels are just one tool in the RPG shed. A good one, but abused in MMORPGs. Making the journey more important can be made better by also making the journey more entertaining.
And by not only making level less important, but in many ways, gear. In fact in many ways I don't think that gear should be tied to level. I think that any level should be able to use any gear. If anything should be done to prevent higher level gear form being used at lower levels, it should be that higher level characters get exponential stat bonuses on gear. Locking gear to a level is completely illogical.
It makes sense from a gameplay standpoint, but not from a lore standpoint. And there are better ways of preventing overpower caps. Like, again, higher level characters using the same gear more effectively and getting level bonuses. No other RPG genre has level caps on what level can wear what gear.
Back on the subject of levels, I think that not only do levels need to become less important. But I think that a clear and defined "endgame" needs to disappear entirely. A lot of people decry the "sphere grid" system in Final Fantasy games. But MMORPGs are one of the few genres of game that I think something like a sphere grid would be a huge benefit.
A true endgame really would be impossible to reach, if, instead of having a endgame levelcap of something like 50 or 75, have thousands of little nodes to fill that were more important than your level. And make not so clearly defined transitions in the game. When you're at a certain point in the game, you know it. And I feel like that's a flaw, takes away mystery and desire to explore and discover.