I think a lot can be said about some of this content just being new for Legion, but I think a bug factor for BfA is that some of it feels like a stripped down/worse system than what was in Legion.
The artifact weapon system made sense, unlocking the potential of a legendary weapon makes sense, soaking up crap in a necklace just so you can use your gear is a much less elegant system.
WQ's and Mythic+ were new, but by the end of Legion lots of people were tired of them. Myself I was just done with the timer system that is Mythic+ and haven't done a single one in BfA. If you want something to be hard then make it hard, stop with this go go go as the means to difficulty.
I think also with them removing unique sets, tier bonuses and other things, well there is little motivation to do some of these things.
Classes are dull and I'll be the first to admit I liked the fact that on DW classes in Legion you finally didn't need to get lucky with upgrading two weapons.