One of the biggest issues with BfA is that most of the "systems" content was just copy-pasted from Legion with no improvements or changes for the worse. The "new" systems of Islands and Warfronts were both pretty big busts and likely ate a TON of resources for completely underwhelming content. Those aren't even really that novel anyway besides some of the AI tech, as they're both using the scenario framework developed in Mists.
When you also account for the loot situation being objectively worse than Legion as of 8.1 still (losing Legendaries, Artifacts, and Tier Sets for...Azerite?) and other things like professions being absolutely gutted and mostly worthless except for Alchemy (Alchemy has always been quite powerful, but other professions are WAY worse than previous expansions) it's just a mess. Some other things as well, but it's all been covered before.
There's a theoretical large amount of "stuff" to do, but not much of it is actually fun or engaging. And everything showers you with loot now, whether it's appropriate for that level of activity/time investment or not.
I'm not sure if there's an easy solution at all, since you pretty much have to be revamp almost every system in the game right now, an expansion-level effort, if not greater. It's clear Blizzard was really pressed to meet a deadline with BfA and they couldn't even do much by 8.1's release to change course. It'd be interesting to see an extensive post-mortem later, as whoever signed off on most of the stuff that made it live clearly didn't have a good understanding of the game. There are many potential points of failure though, so you can't just lay the blame on a single person at Blizzard, even if it's easy to point to some more public figures that probably aren't doing their jobs well. The whole scrap and re-invent the wheel thing every expansion for the past few expansions isn't helping when there are reasonable solutions that were implemented IN THE EXACT GAME THEY'RE WORKING ON previously. Like the developers haven't even played much of their own game, understanding what made it successful, which kinda makes sense, as I imagine most of the designers except maybe artists from earlier expansions aren't even working on WoW anymore 14+ years of development in.
But if that's the case, they really should sit down and just spend at least a week or two in WoW history class or something, or actually engaging heavily on live servers (or earlier iterations of the game, private servers if they don't have functioning older internal builds.)