I'm glad I'm not the only one who thinks that because I was told elsewhere it was a spicy take.
The zone storylines tend to be good, hell even the concurrent/conclusion storyline (Zandalar Forever/Rescue Jaina) can be good.
But whenever that stops and we go back to the "main" plot with the pre-existing characters starts back up, the quality swan dives into a shallow pond. It was like that for Shadowlands too, I thought the individual chapters of the levelling story were a neat introduction to the expansion, then I hit level 60 and we were back to Sylvanas and Bradd Pitt being sad and I got bored.