I'm genuinely surprised to hear this. When Legion launched, many retail gladiators including Weafy, Sin, Praii, and MANY others came to MoP servers because of how much they loved S15. Even now we have retail players that came in the last 3-4 months and what they have all told me is that they came because of their love of S15. Ironically enough, WoD was pretty universally hated for its arenas, overshadowed only by the hate Legion got.
I don't know the PvE scene nor the dailies, but arenas in MoP is the most fun I've had ever doing arenas (and yes, I've done them quite extensively on all the expansions except Legion).
Honestly, when it comes to PvP I don't know how anyone can take Wotlk seriously for PvP anymore (outside of Blackrock, which is definitely equal, if not better than Frostwolf). Icecrown/Lordaeron is a competition of who can raid or donate for their gear, while arena teams result in a terrible logistics competition of who can manage to gather their teammates on time more often. On top of that, Random BGs are run over by BiS geared characters deleting lowbies trying to gear up, because they have nothing better to do (like Rated BGs).