I'd say mostly around 88/89 was when that stopped being the main focus, but yeah.
They were so big because they combined impossible, imaginative events with human drama. It both acts as a window into the supernatural and as a character study. Kids can both have a sounding board for their frustrations (why doesn't this girl like me, why am I not accepted, why are people so unfair) while also experiencing issues they don't personally know and get insight into how other people think. It's also entertaining to adults because of the common dramatic irony (Peter blames himself for all the wrong things, most of the X-Men are hypocrites, etc) and the soap opera structure. And then the weirdness and action is great when juxtaposed with this, as it gives weight to the drama and breaks up the monotony.
Shame how the people running the company don't understand what made their books sell.