WoD started and Legion continues pruning. I suppose abilities of all types have been pruned, but what we really feel the most is the pruning of abilities that don't directly contribute to damage rotations, of which there has been a ton. We feel the loss of a unique spell much more than replacing or combining a couple of nukes.
This trend is very bad for pvp, which really needs lots of interesting abilities that aren't purely damage. Abilities like grounding totem, spell reflect, curse of tongues, curses in general, gouge, dark sim, and many more. Even simple choices like which armor to use (fel vs demon) are engaging in pvp. Some of these abilities come back in pvp talents, but you're only able to pick 1-2, rather than the 3-6 (or more) that kits used to have.
Without these abilities, pvp feels like a damage spam. In the past, it was the case that pvp battles were significantly more complex, in terms of the types and number of different abilities being used, than pve battles, even raid bosses. However, with very significant pruning of non-damage abilities, and pve fights getting ever more complex, this may no longer be the case. It may be true that raid boss battles now have more going on than pvp, and that makes pvp dreadfully boring (since it's lacking other things that make pve interesting). Even if it's not true that pvp is less complicated than raid bosses, think about the weight that puts on players, backtracking in depth so far. What if the first raid of Legion was equivalent in depth to vanilla Molten Core? People might not be so happy--yet that's basically what's happening in pvp.
The result of removing all sorts of different non-damaging utility spells and replacing them with 1-3 pre-boxed pvp talents is that pvp starts to look like a moba with really complicated (for a moba) damage rotations. You might say: that's not so bad, mobas are really popular. Yes, they are very popular, but WoW's pvp audience wants to play WoW pvp, not a moba. Worse, WoW pvp looks like an extremely watered down version of a moba, missing all sorts of incredibly intricate and interesting elements, like map positioning, farming, ganks, on-the-fly-builds, map objectives, etc.
I understand you're trying to make the game more appealing to new players. I share the concerns of making WoW (and pvp specifically) easier to get into and easier to watch on twitch. But it does nobody any good if those new players have nobody to play against. WoW pvp needs kit depth in utility and non-damage abilities.
For me, abilities like Dark Simulacrum added a great level of depth. A friend of mine loves the ability and the freedom it offers: do I need a heal? Let me put it on a healer. That mage is probably going to Mirror Image, let me steal that. That sort of stuff.