Dota and WoW have been popular amongst teens and young people for as long as I can remember, so considering that eSports betting has existed for a long time already, I think the number of involved players we see now is at its peak. Moreover, it seems to me that these games are becoming even less popular these days than it was before. At least that's what I've seen, maybe I'm wrong about this.
The boom of MMORPGs started during the time of early 2000-2010s where every kid visited computer shops and cafeteria to play with friends. Nowadays, with the development of technology, most kids have migrated towards playing with people from their houses (especially this pandemic).
The problem with most MMORPGs today is that, every game has been recycled all throughout. No innovation as to questing (typical "kill 5 slimes") and the experience nowadays with new MMORPGs have been stale. I do hope that in the future, new games would introduce new systems in order to be innovative and stay on track.