I love how this is the narrative that people go to, yet there's no real grounds to support it. Destiny PvP is so different from other games that players who play other PvP games likely wouldn't want to play it no matter how much SBMM you'd apply. The looter nature of the game and the inherent lack if balance compared to competitive shooters as well as the high cost of entry and PvE grinding required (as well as the controversy of DCV) means that people who play Apex or Halo or whatever often don't even think about going into Destiny because it's a completely different kind of game.

For the actual Destiny playerbase, PvP in Destiny is fine. Matchmaking is quick in basically every mode. Iron Banner and Trials are always full. Control matches get filled in seconds. Warmind.io stats show that the Crucible has a healthy population cut, even towards season end.

But somehow the population is stagnant, declining, PvP is in a horrible state and only hardcore keep playing it. Sure. Or maybe, there's a loud group of PvE players who like to complain on reddit because they don't like how Destiny PvP plays. I guess we'll never know.