You're on the right track. Bungie got a ton of negative feedback on the increased difficulty of the game, and a lot of the difficulty they have added is really just the feedback of longtime players like content creators feeling like they never have any challenge for a game they play endlessly. If they're not getting one shot by everything they feel zero challenge. But that's not a healthy thing to create for any game. The players needed to move on once they conquered it.
Look at the Monster Hunter community. It's a totally different vibe. I can solo several of the high end monsters and rarely need help but there's people that can't get past their first elder dragon. But they can get there. Solo. As long as they try. The game scales with more people. Even right now MH World has more concurrent players than Destiny 2 and the game has been pretty populated and healthy all year. They don't develop every single piece of content to GM level, they have special fights and leave it at that.
I have next to nothing to do as a solo player. I brought friends in and they felt nickel and dimed by this game, and bounced. I felt like a fool. And Bungie doesn't care about me. They're just like, thanks for the extra dough dummy, buy this skin now that you played one mission. Everything about this game when you login now is: please throw your money at the screen. That worked when we wanted to, but we don't anymore and they don't have a clue what to do.