WoW is not a niche MMO-RPG, but MMORPG as a genre is a niche for gamers and gaming, in 2021. And it has been like this for 6-8 years. People still hang on the ideea that WotLK had 12 milion players and the rest of xpacs were bad, but in fact those players got feed with the MMO genre, they are playing other GAMES, not other MMOs. At least this is my perception of how things work. All games have a start and an end. All genres have a start and an end. We used to like to play simple FFA games like Quake and Unreal, but not anymore.
Just as XCOM is a game representing a nich turnbased genre.
When a genre is actual and looked for, many games are produced. Look at BattleRoyale genre. MMORPG’s peek era was 2000-2012, but for the moment no one wants to develop an MMORPG, just like even Overwatch was reworked from MMO to FPS.
I love WoW, I played WoW as a lifestyle, not as a game that comes and goes.
Even in its worst states - (BFA) - , I still had my sub active more then half of the time.
But even for me, personally, I can feel, I don’t want to be involved in playing the best MMORPG (WoW) because as years pass, they are feeling shorter and shoter and my time feels precious and precious, I can’t sit half of my available gaming time to watch the LFG window and try to get a couple of 2s games going.
Once the kids will find their own paths, and be like 10-15 years older, I will probably start playing WoW Classic and ride all the xpacs head to head. But until then, I really wish #soloqueue was in WoW, or another game appears and has WoW’s extraordinary gameplay and mechanincs and 2s Arena solo queues 
I’m not a forum guy, never been, 48 posts in 16 years shows that. But now, I really love SHADOWLANDS and really wish it would have a spot for me, since I am only playing PvP Arena 2s (NOTHING ELSE). In SL I didn’t complet not 1 M+, did only 1 Heroic Dungeon since I had the bastion covenant quest. All i want is to LOG IN, do the weeklies in 1-2-3 hours, and just do arenas. This expac is not forcing me to grind anything else, not forcing me to gear only in PvE just to be PvP ready. It is a great xpac, and not having much to do and leave me just to play over and over the part I want to play, puts this xpac next to TBC and WotLK, FOR ME. But at the same time, out of 30 days of /played at lvl 60, more then half of those played days are representing me sitting in Oribos and looking at that LFG window :(.
GL HF