MH has so many characters who experience various symptoms that are extremely relatable to people who are disabled or otherwise experience troubles. Robecca's time blindness, Lagoona 's excessively dry skin, Draculaura's aversion to blood to the point of fainting, Clawd's excessive hair loss, Venus's seasonal affective experiences. I wouldn't necessarily say all these characters (along with the many others) are "canonically disabled" - but there's something very fascinating and comforting about the relatability. That even if a character doesn't have your exact diagnosis you can find parts of yourself in them.
Not to mention how EASY it is to get accommodations in MH. There's no fight. You mention you struggle with something and the reaction is almost always "oh really? Okay here's something that may help."
It's all tied to the diversity of monster types and their different needs of course. But it can resonate with people IRL too.
I've wanted to do a video on MH and disability for a while because I think it's really interesting. But I'll probably never get around to it.
Feel free to add any things you've noticed and found particularly relatable.