I've been playing since Vanilla and the grind has never ever been this bad, and the reason for it is mainly the AP and the RNG elements which make everything a chore.
To put this in perspective, back when I was grinding endless scourge in the cauldron fields it was optional, I wanted the AD rep so I did it, none of the grinds in Vanilla were really mandatory to do well at the game (apart from doing dungeons/raids for gear but that is the game). Then came TBC, of course I grinded dungeons for badges because some of the gear was useful, and I got it. The same happened in WotLK, each tier new items to work towards, it gave a nice sense of progression even when playing solo. The system was improved in Cata and then again in MoP where finally you could even use the points accrued to upgrade your items.
Then in WoD I would do the apexis dailies and later the Tanaan stuff, because even though they were grindy they gave me currency I could save up to get an item or slot token that I wanted/needed and then upgrade it.
Now in legion I do WQ's in the vain hope that RNG will shine on me and the junk reward will somehow titan forge to useful, and as an extra bonus if I do four a day I have a RNG chance to get a legendary item which has a further RNG chance to be useful, there is no goal, I am not working towards anything and the directionlessness makes the grindfest even more boring. I have to remember never to change my loot spec to get any off-spec items though or I may end up with a useless legendary thus screwing myself over.
Add to that the AP scenario, where how good you are at your role depends on how much AP you have farmed (in addition to how much gear you have acquired) and no wonder so many people are burnt out, the game is the grindiest it has ever been in it's entire history, and it sucks.