You've nailed it.
-A Smaller world.
The giant world in Breath of the Wild worked for what the game is, but I don't think every Zelda game needs to be this big, future games should have worlds about 3/4 to 1/2 of the size.
The dungeons in BoTW are cool, but they are just so short and they all share the same visual language. I think 8 proper dungeons all with their own unique look would be perfect. I also don't want to them to throw away the ability to move parts of the dungeon like in BoTW, so that could be implemented into one or two of the dungeons or maybe just specific rooms in a bunch of them.
-Fewer shrines, and more visual styles
Shrines are awesome, but I think 120 is a bit much, with a smaller world and more dungeons I think 60-80 would be a better number. The fact that all of the shrines use the same visual style is kinda boring, so I'd hope for that they'd have a small pool of visuals styles that they could be, like cave or ruins and they could even steal some styles from the dungeons as well. I'd also like more of the "shrines" to be integrated into the world, or instance as an actual building or cave that you find. It'd also be nice to have more quests associated with certain "shrines" beyond just finding them, so stuff like save a kidnapped villager from some Bokoblins in a cave.
-More interactive bosses
While the dungeon bosses do still have a bit of a puzzle element to them, for the most part the bosses are just combat challenges now, and that's fine! But the bosses just don't have enough behaviors to be interesting. I think they should look a how Dark Souls does its bosses, and no I'm not saying make them that hard, but just look at how they have lots of moves and behaviors.
-Larger enemy variety
BoTW has a pretty small selection of enemies and that's kind of a bummer. There should be a mix of new and returning enemies (like Deku Babas, Skulltulas and Darknuts) in the next game.
-More overworld bosses
Having bosses in the overworld is pretty cool, but there is only a small few bosses and they just get variations. It'd be much more interesting if there was a wider selection of bosses, some could even be based on dungeon bosses from past games.
-A bigger focus on story
Zelda almost always has charming writing, but because Nintendo treats the story as less important than the gameplay and design very rarely does a Zelda game feel like it has an actual good story and I feel like that's one of the franchise's biggest weaknesses. More time needs to be spent on the story and with the characters, why should I care about someone like Teba that the game tells me is important but leaves the story as fast as they enter it?
The small towns worked for BoTW, but for future games I would like to have larger towns with more people, more sights to see, games to play and more quests. Not all towns need to be large mind you, but at least some. It'd also be nice to have a city or two.
-More involved quests
A lot of BoTW's quests are busy work and there isn't much in the way of actual quest lines. The next game should have more quests were you have a real goal and quest lines, for instance you could join a guild or something like in Elder Scrolls, or you could do interconnected quests for a group of people that builds an enjoyable, self contained story.
Again, BoTW not really having a villain worked for the game, but it's not something they should make a habit of. I want a new and interesting villain with goals beyond just becoming the supreme evil overlord of the world.
I enjoy the durability in BoTW, but it would be nice if you could take a weapon to a blacksmith to repair it before it breaks, maybe you could even have weapons reinforced to improve their durability.
-Permanent mounts other than horses
BoTW allows you to mount a small selection of creatures, but none of them are able to become a permanent mount other than horses, not even stalhorses. If you can mount it you should be able to keep it. The number of mountable animals should also increase, for instance Ostriches and Moose.
Bringing the underwater in would add a whole new level of exploration and discovery.
BoTW is fairly normal, there's some weirdness here and there, but nothing on the level of the toilet hand in Majora's Mask and Skyward Sword. Nintendo shouldn't be afraid to get weird with Zelda.
This is just what comes to mind right now. I love BoTW and feel like it sets Zelda on the right path, but a lot of work needs to be done.
As far as dungeons go I'd like them to be A Link Between Worlds style. Take ~8 dungeons and split them into two groups of ~4. Complete the first ~4 in any order, then the next ~4. I feel like the progression of dungeon difficulty can't be there if they're all available from the go.