Don't misunderstand me: It will be definitively be better than gutter trash of BfA, but i think that Shadowlands might probably be a bad expansion; around the same as Cata. Because really, i feel a sense of cata-vibes right now:
1.) No connected Zones. That's one of the really bad things that is a repeat of Cata, and to a part also part of BfA: Instead of having one connected land mass, we have 5 different "isles", disconnecting us from them. So we have a main hub like in cata with portals to the different zones. It disconnect people with the land mass and the zones. Even worse: in cata at least they were connected with the continent, here we don't even have this. So for me the zone design is actually worse than Cata.
2.) Absolutely no features. So what we get are new bloated factions, something like lazy order halls, just as they did it with tier sets (that are not returning); instead of doing it for all classes, they rather broke it down to 4 factions. And the rest: The maw and the tower of the damned are both diablo-esque greater rifts, nothing more, nothing less as far as it is known right now. But since the zone-design describe the maw as quite a dead zone, i'm not really looking forward for this being the endgame-zone compared to suramar for example.
3.) No new classes - One of the most stupid things i hear on this forums are: blizzard needs to balance old classes rather than adding new ones: Sorry, but that is utterly, utterly bullshit. If blizzard for example wouldn't revamp classes on every occassion, making working classes where most people are happy (shadow priest pre-voidform) replace with total crap and then prune the hell out of them just because 2-3 players complained that there are too many buttons, and try to trim classes towards PvP and e-sports, then we wouldn't have this issues. Sorry, but thinking that nowadays adding a new class and balancing existing ones are not possible is totally idiotic. It's lazyness (and saving money) that makes blizzard not releasing new classes, not that they haven't the ability to balance 13 instead of 12 classes. And most of all: balance towards PvE, but do not try to make every class-spec performe the same in PvP. WoW was, is and will always be mostly a PvE-Game, only in times where blizzard focused mostly on it, especially not balancing towards e-sport-gamers and towards the upper 0.1% of the playerbase, WoW was the most successful.
4.) Zone design: Maybe it's just me, but from the videos i've seen, Bastion is a really, really underwhelming zone. Maybe it's because it is so unfinished, maybe the bad lighting (that is hopefully by far not finished) or maybe the bad textures and models, but right now it seems like a very, very bad zone and underwhelmingly small too. We know nothing about the rest (except the maw from the videos with the jailor), so it might hopefully get better, but Bastion, the first zone we will go to will really be quite a bad zone.
As said before: Will it be trash? No, but still i think that shadowlands will be in worst case a bad, in best case an underwhelming expansion. Just my personal opinion.