When an MMO launches it normally has little content and uses difficulty to pad playtime, especially subscription MMOs like WOW and pre-one tamriel ESO. Typically an mmo reduces difficulty of old content over time, when new content becomes available.
I do agree that the effect is much more pronounced the more popular a game is. LoTRO at least added some of the overworld challenge back with an optional difficulty slider after community backlash, and I'm not sure that a less niche game would have bothered.
it is a well known industry standard design philosophy.
https://arstechnica.com/gaming/2021/09/too-much-of-a-good-thing-mourning-the-slow-death-of-the-retail-game-store/
https://en.wikipedia.org/wiki/Nintendo_hard