Wow atm is boring, dull, very easy and everything is handed to you once you reach max lvl. Some stuff i would personally love to see back and im sure it would benefit the game:
-Attunements: they gave you something to work on when you dinged max lvl, it hyped up the raids and gave them more value, it made you travel all over the world and through dungeons to uncover a story and made YOU an important part of the story and it was just awesome. Now when you ding max lvl you imediately jump into LFR, the raids dont feel epic at all, you can leave the raid whenever you want with little to no penalty, its boring.
-Farming for stuff at max. lvl: what happened to farming, i remember in vanilla and TBC ppl at max lvl were out there in the world farming stuff either for raids or to craft an epic or something, now you have everything you need, nobody farms anymore or they use bots, farming made the world feel alive, it also gave you something to do at max lvl, it made you meet other players from your realm, creating rivalries and spontaneous world events.
-40 man raids : the more ppl you have the more epic the feeling, i know most of you will say that its hard to recruit and coordinate 40 ppl, but back in vanilla there were guilds that did it succesfully and we had world firsts competition aswell.