I agree, I think cata overall was the heyday of pvp, despite competitive wow having died after s8 (mlg dropped it and then it kinda just faded from there, now all that's left is blizzard's championship series every year). I never pve'd in cata so I can't say much for that, although I agree that the lore had a ton of holes and WTF moments, but it was a story never before told in warcraft or any novels, so it wasn't as well articulated as something like the story of Illidan, the Sunwell, or the Lich King. MoP was basically cata's ugly younger brother, the PvE wasn't tremendous, the lore was pretty eh (excluding the side stories, Vol'Jin, Wrathion, Taran Zhu, etc. I thought those were pretty cool) and the pvp was god awful from the get-go and never recovered (see: Mitch Jones' Big Numbers videos or Reckful's video of Pam playing his warrior at 2.4k rating).
While I thought wrath was great, I really never was any good at it and going back to learn it now would take me weeks of time given the time I have available to play, so while I downloaded it and play it from time to time, I really can't enjoy it as much as cata simply due to the fact that I'm hopelessly terrible and get destroyed whenever I set foot in an arena, whereas in cata I played a ton and got pretty decent at pvp (iirc i was around 2100 mmr on bloodlust US, and 1900something soloq on AT) so I can do fun things like playing 2's with warglaives on, simply because my understanding of the game and mechanics/cooldowns and such is so good. I'd really hate to see that go, but meh. I'd probably just put wow behind me altogether and learn a new game.