I said a bad expansion.
Wow has had: BC, WotLK, Cata, MoP, WoD, Legion and BfA ... that's 7 expansions. So the fact that I consider Cata and WoD to be worse, I can't say it is "one of the worst" because that is nearly half of the expansions at this point and we know not a lot about Shadowlands just yet.
So, it is bad. The story was all over the place, there didn't appear to be one writer or one person over the writers controlling the whole story. Plot points moved way too quickly for my liking. It would have been nice to have the story spread out more. I do like that the fact N'Zoth was hinted at since the beginning ... it was minor, but it looking back that was clear where things were eventually heading and the only question was were we getting N'Zoth in BfA or the next expansion and obvious that is BfA. And given how N'Zoth was treated, it makes sense he would be more behind the scenes until his final move.
I am not yet certain if I put BfA above or below Legion personally just yet. It is clearly better than Cata and WoD, but clearly worse than WotLK and MoP. BC gets a pass for me being the first expansion so there was clear growing pains there, but I also would place BC higher.