I like BfA and think it's a good expansion so none of this is hating the game, just answering the question with my opinions. You can like something and still think there's room for improvement.
There's too much focus on RNG shit instead of letting people control their progression. That is one of the big mistakes of this game. Another thread that lasted for a long time had a title that got my attention; There is no difference between a 8/8 and a 0/8 character. There's not much when it comes to goals you can steadily work towards. And because of that there's not much room for looking at the other guy who's actually accomplished something and being motivated, which kills the MMO feel. Just do your randomized dungeons or every other WQ to get your randomized ilvl gear and ignore all other content. Drains away the feeling of progression when it's all based on rolling some dice.
Another thing that contributes to it not feeling like an MMO to me is there's nothing to do besides instances. Professions are pretty much worthless. A few WQs are worth doing to, as usual, roll the dice for BiS rewards but that's it, most are best ignored. World Boss drops are in the same situation, try to roll the dice again unless you already got a piece for that slot with higher ilvl or the right stats then no reason to bother. No badge drops or good rep rewards to encourage you to do content out there to steadily work towards something, nothing, no reason to do anything but go into instances and roll some dice.
Last thing that's wrong but I came to realize it lately but didn't feel was a problem before is there's no content besides combat related stuff. The game's always been like that and I was ok with it but playing other things reminded me there's so much more to do in other MMOs that actually end up encouraging me to interact with other players, like mini games or actually interesting crafting systems, or housing systems. WoW is just combat and nothing more. Even back in '04 there were MMOs that could let you do more than just that. But that's just something I've only come to notice lately, I was ok with it for years so not really that big of a deal I suppose.
Everything else about the game will change or be patched. Class changes, ability changes, they come and go. But what I've listed have been changes in their design philosophy that seem to be here to stay and that's a shame.