Its an okay expansion so far. I liked the leveling experience for the first time, it has its goods and bads. Doing it on more characters quickly turned into a slog though. At least reaching max level is pretty fast and they give you more options after your first character did the story campaign. The zones feel few and the terraining is just awful, probably some of the worst they have done yet. As for the zones themselves:
Bastion - Looks beautiful, good music, awful questing
Maldraxxus - Looks bland, decent music, decent questing
Ardenweald - Looks good, beautiful music, bad questing
Revendreth - Looks good, bad music, great questing
Then we get to the Maw... which feels like a zone where they had no idea what to do with it and just slammed some random ideas that may have sounded good on paper (the Jailor fucking around, no mounting to make it feel more threatening, being in constant danger), yet it turned out to be this expansions worst feature. At least you can choose to just ignore this zone. Torghast was imo fun with the first few runs, then it got boring fast and the time investment and reward is just not worth it. Its not exactly fun that I got a boss at 1% (one of them was at literally 6 HP), ended up dying and didn't even get anything out of it. At least I got Bolvars quest done. Both the Maw and Torghast are more frustrating than fun, and if Blizzard doesn't change them then I doubt that I and many other people will even stick around for them.
The covenant system isn't as bad as people were making it out to be. I think its funny how things got revered this way: people thought Torghast was going to be a lot of fun with endless amounts of engagement, while thinking that covenants is impossible to balance and people will even not allow certain players with the wrong covenant in their groups. Yet the opposite happened where Torghast quickly became a borefest and covenants are just alright.
What else does SL even offer... nothing really. No new class which really needed to happen. I guess their core content like dungeons and raids are alright, but other expansions did them better. Gameplay still has issues, PvP got better. Overall I would rate it above Cata, WoD and BFA. Below TBC, WotLK and MoP. On par with Legion.