Do you really need new things completely new things to enjoy an expansion, iteration and improvements can make the game feel fresh. Covenants is an iteration of the class hall/campaign which was widely considered successful, whilst the war campaign seemed less like that system. The gameplay elements like the soul bonds are new so it should be really fresh. Torghast could be considered an iteration of islands but the gameplay is different, and has ties like craftable legendaries which is an iteration of a system that effects were widely enjoyed but attainment was flawed, which is good. It also supposedly won't be timed which is something people have wanted in content. The maw is an iteration of an endgame zone where is supposed to feel dangerous and scary (no details so who knows if it will be good or terrible.) We don't know about gear or WQ changes and the degrees they will be. The probably biggest "new" stuff is probably the lore and environment where there's nothing really written about the characters/ cosmic elements of the shadowlands and it seems there will be some plot twist or shock with the jailor being a new character, so who knows what is in store.
I am sure I am not the only one who is not hyped a single bit. I will wait to see how things have turned out and maybe I will return to WoW. But for now, all SL features are seriously lacking on paper.
We already had craftable legendaries in Legion.
Isn't the ability to choose from a pool of items in your Mythic+ chest coming as well?
I was going to say disappointment but that's not really new now is it?
Nothing interesting for now.
I guess in the same way that the arena system is just a glorified BG. A one in four choice that gives you two abilities, a mini talent tree, and various world benefits isn't very close to reputations repackaged. Particularly when we don't know anything about the time investment with them beyond each having a campaign.
You want a new feature with a fun loop, I want quality content and my type of content is story.
If you just keep adding new features, the game will get bloated. Now, Achievements, Transmog and such do not bloat the game because they aren't mandatory for progression but see for example Island Expeditions and Warfronts and Timewalking. They are new features with their own loop. You do 3 mythic islands every week on one character and Warfronts you do twice a month, Timewalking you can do once per 3 weeks (for the big 500 badges bonus) and so on. Now when you have all those align in the same week and you play multiple characters.... it's a bit too much. On those weeks I have to several hours every day. It's a bit too much. Adding new features is nice but it's not all about innovation and fun loops, a major factor in the design choice is "does the game really need ANOTHER time-consuming feature?".
Which is why I am happy with "content" instead. New layers to progress through for already existing features. Namely, new raids, new dungeons, new story. And make it a "quality" thing with improvements like the one we saw in Suramar.
Suramar was merely a glorified reputation but it was so much better and more immersive than anything before or even after. Content like that can keep players occupied and immersed for a long time. It's good for the game. Also, your desire for new features and my desire for new quality content do not contradict each other so... why not both man :P And we do get a new feature in Shadowlands. Torghast. It is an iteration of all the previous solo play features such as Mage Tower, Horrific Visions, Withered Training, Isle of Thunder Vault, but still. It is a fun loop. It provides a new game mode (solo) and can be actually difficult and immersive. And when you do the "does the game really need this feature?" I think it well passes because of how much positives it brings. I don't know what else you could want mate.