There are many things wrong with BfA, so they can't possibly fix them all. I understand that. And they should dedicate a lot of their resources to Shadowlands.
But how do they get away with basically abandoning SUBSCRIPTION-based game for many months before releasing an expansion? So the deal is, you keep paying us money and we'll just do nothing for the product that you're CURRENTLY paying for. If you'r charging for the expansion cost and a subscription, then you should deliver appropriate content and fixes for it for the full duration of the expansion.
There are many things they could do that wouldn't even take that much effort. Make essences account-wide, make corruption offer more options from your weekly mythic+ chest so you can choose the best option. Blizzard themselves said they're doing this in Shadowlands. But they decided that no, we're going to leave it as it is in BfA, cause the quality of life for people playing now doesn't matter (but please don't unsubscribe though).