Lots of people that play World of Warcraft claim they don't raid for power (i.e. gear). They say that. They said it for years. Their behavior made liars of them then, and it does now. Asmongold's video below explains why:
People will take the path of least resistance. Gear is power at endgame, so people will take the least resistant path to gearing up. Once geared up, they will use that gear to exert dominance over others in PVP--instanced and open world--and try to be the biggest badass around. This is observed behavior going back to 2004 just in World of Warcraft.
So yes, when presented with a faster path to Real Ultimate Power, the vast majority of players will take it. To stay competitive, the raiders and the PVPers have to do it too- and better. It's no secret raiding's degraded, and the top-end declined, since Cataclysm brought in Looking For Raid (and before that, with the 10/25 split in The Burning Crusade), but there were sweet fuck-all for viable gearing paths until now. The results? Not hard, and contributing to burnout issues to boot, to foresee.
So, what do?
You back the fuck up immediately to the last stable iteration of the thing. That's not a gaming thing. That's everything. When shit breaks, you revert and remove. This is why you do NOT fix what is NOT broken; you just fuck it up and cause far more problems (costing you time and money while customers dip the fuck out for unbroken competitors) than you ever expected. That the developers for World of Warcraft--some of whom have been there all this time--still haven't figured this out (when I got it back in fucking elementary school makes me wonder just how competent adults in general are. (I am not confident.)
So, what was the last stable state for endgame power progression? Overall, it's been a mess since they got away from Raid or Die, so that's where you revert to and you remove ALL options that don't require raiding. Endgame crafted gear? Requires materials only gotten from raids. Gear drops from bosses? Only in raids. You get the idea.
This means restoring the original play paradigm (that got junked early on, sadly): you raid for gear to get the power you need to dominate in PVP to establish control over vital resources in the open world and maintain access to instances (and the teleporters go away; no more LFR or Dungeon Finder, leaving only the Group Finder- everyone has to go to the open world locations to access the instance). This means making all of the servers one type so everyone plays by the same ruleset: PVP. (Ideally, RP-PVP, with very strict rule enforcement.) The ability to soft-merge all servers already exists, so we do that and solve the population problem both in the short term and with one policy change (strict faction population limits per server) in the long term as well.
To truly fix the game, you have to eliminate leveling and make endgame THE game, but that's for another post.