I always assumed Fairy Tail was propped up by a more casual audience aside from the ones who are there for boobs.
Which isn't meant to sound derogatory or anything as far as calling people casual goes; it's just that I seem to see very little positive reaction from the people who go out of their way to post about anime and manga online.
Maybe it's just the places I frequent though.
In all honesty, if I was younger, I probably would've given in cuz "OH BOY, ACTION
AND BOOBIES, JUST WHAT I WANT IN MY MANGA!!" was on my brain as a teen. Probably why I somehow read through Negima for a good amount of time before it went into time travel or whatever.
But yeah, it seems to be one of those "gateway" anime for this generation (see also Attack on Titan), sort of like how Naruto, Inuyasha, etc. was for the mid-2000s kids. It's generic to us who've seen a ton of anime, but it's still "new" & "fresh" to those who are still being introduced to anime in general.