Outside of raids, MoP didn't have any endgame content to keep people busy. Timeless Isle is overrated, and it's BfA version, Mechagon is far superior by design and mechanics. I didn't have that problem, because i was always ach hunting in downtime, but sincerely, outside of raids, i only remember farming that elite Zandalari mob on a boat near Dino Isle, thanks to the early iteration of CRZ. And that is it. Dungeons were super easy, and people only did Challenge Mode once.
People here are vastly underrating the effort the devs made with Legion and BfA. I was redoing some old achievements in the last year, for fun and nostalgia. I would concentrate on one expansion for a month. It confirmed to me that people have a severe case of rose tinted glasses. Up to WoD, most of content were painful dailies. Molten Front dailies were annoying to do even at 120. Wrath tournament dailies, horrible, even at 120. Sunwell dailies? MoP dailies? Same, both painful to do even at max lvl.
I also love how people are all of sudden praising 7.3, while at the time, hell broke loose because of no flying.
BfA gets a lot of hate not because of the systems - it improved on those coming from Legion. I actually burned out of the game in Legion due to AP farm, and i can't understand people who say HoA is worse - it isn't, by a long shot. I love not being locked into a single weapon anymore. There was LESS time gating in BfA compared to Legion (weekly gating on Suramar questline, anyone???)
No, BfA is hated because wow players don't like ''disjointed'' expansions, because the theme felt less epic then Legion and because of stat squish and new scaling, people felt less powerful. Combined with the rise of ''outrage culture''.
Also, BfA is overall more difficult than Legion (imho Visions blow Mage tower out of the water with difficulty), and once again, people didn't step up (as they didn't in early Cata, so they left en masse).