People hate on survival because blizz destroyed one of the most enjoyable specs in the game (Surv MoP-WoD) and flipped it on its head.
Survival today plays wonky, yes, and has decent damage thresholds, yes, but it's a sore spot for a lot of people who were forced into boring ass BM or MM because they wanted to play ranged, and let's be honest, tons of mechanics favor ranged anyway, and with the influx of DHs and such, melee is typically crowded as is.
Add in surv having a higher skill threshold due to a lot going on vs BM's "bash buttons lul" and MM's "expose/AS smashing with stagger steps" and it's no wonder why it's the least played this xpac.
The cherry on top was taking elements from surv (ES, LnL, BA), but changing them to trash and giving them to MM where no one really uses them.
You still have 3 specs that play a little differently (BM being instants with pet, MM having cast times (no pet, which is still weird to me to this day), and surv being john fkn madden), but all a lot of hunters wanted was old-ish Survival run and gun and fun.