Islands feel much better than pre 8.1 They still are what they are, Which is run around and kill stuff. Nothing wrong with that but adding variety to the events on the islands would be nice. More things like missing the other team or islands full of giants (both mentioned at blizzcon) are needed.
Also a variety in the activities on the island. Killing mobs is great, the variety and abilities of the mobs are fairly different. But a lot is still avoid this aoe, or that aoe, or make sure to interrupt the heal. I think adding things like the Legion Kiring Tor World Quests would be a nice addition. Maybe they dont phase you into the puzzle and mobs or the other team can knock you out. Even the shell game or bejewelled or any of the other minigame type toys would be great to find randomly around the island.
Some really well hidden treasure chests that require some interesting platforming would be cool, and classes with extra movement abilities would be able to utilize them in an interesting way. Or the quests, instead of finding the key why cant rogues open in? Why cant healers cleanse the poison from brunhold?
I enjoy the difficulty of the higher islands and the chance to get one shot. It does feel a little extra punishing to be missing either a healer or tank in mythic. It feels like you cant pull fast enough to keep up with the other team, or at the least it leave very little room for error.
It can still feel like there maybe are to many weak mobs that make the pulls unruly and AOE fests instead of interesting fights. The more mechanics I can counter to beat the enemy instead of just out dps or outheal the dmg coming in the better.
When it comes to rewards, the weekly is great, the treasure map was a great addition, The rewards on the map are fairly nice, usually. The 2k azerite mission is a good reward, but it is neither fun nor interesting. Also I am a transmog collector, but ill never be excited about random bracers or boots for a set I might or might nor really be working on. The full set, or at least multiple pieces would be a better reward.
From the islands themselves it feels like I am getting less and less from them. I dont mind loot being random, I dont mind not everything be available at the vendor that is from the islands themselves. But there are to many layers of randomness that the chance to ever finish a set or get the specific weapon mog I want seems impossible, let along trying to farm a specific mount.
Personally I really enjoy islands. They still feel unfinished though. There is nothing in them that feels awful anymore (except the rate of drops sometimes). So much can feel better and so much can still be added which is what I would like to see.