Let me just get something out of the way:
Master Mode is the optimal way to play this game -- and naturally, the game's "Hard Mode" was behind like a $20 pay wall. Thanks Nintendo!
ok so the problem with BotW is that it's really good at alot of different mechanics but it doesn't ever feel like it really pushes any of them as much as they should. Ironically, the game's biggest strength and driving factor (weapon breaking) is also the source of its greatest weakness. (Poor reward incentive for actually exploring.) The biggest reason for exploring in BotW is to find things, but everything you find is ultimately temporary, not to mention picked from a standard list of common gear. So ultimately, you get to a point in the game where there's no reason for you to really explore anymore because you've either:
a) gotten as geared up as you ever need to get
b) can't get any stronger because of inventory limitations
c) dont want to try and get stronger because the risk/effort is no longer going to return a reward worth your time.
This is made really clear when playing Master Mode, as the effects of the game's design are amplified by like x10. Everything you find is valuable because everything you own is temporary. But once you get to the point where you understand the game a bit better and finally get your bearings, there comes a point where you hit a progression wall. You realize that there's little value in exploration or hunting for rarities because since you have to use your consumables (everything you own) to actually progress, your chances are such that:
a) you'll break even in your expeditions and mostly have been wasting your time
b) you'll come out worse off as you've broken all your equipment and wasted all your items just to find nothing, or next to nothing
c) you'll come out with a slightly better weapon (or more likely, just a replacement for what you lost) and pretty much feel like you wasted your time.
The only lasting finds in the game are from spirit orbs, armors, and the Divine Beast abilities, of which there are very few. I think what BotW really needed more of was waaaaaaaay more enemies like the typical Guardians. Some much stronger, some slightly weaker, but given enough of a presence that you always feel compelled to be at the top of your game when you're traveling to new areas. Lyonels were neat i guess but there were only a few of them and they were actually extremely easy to avoid since they don't actually aggro you unless you threaten them. There also should have absolutely been more weapons that functioned like the Master Sword, where you can deplete durability but don't actually lose the weapon....or at the very least you aren't left with absolutely nothing once it breaks.
So yeah, if BotW gets a sequel, I think they need to:
1) Add lasting rewards to the map. Not enough to trivialize the survival aspect, but enough to make adventuring in the mid/endgame worth your while
2) Add more viciously aggressive and powerful opponents to the world map, similar to the Guardian Walkers, enemies that give incentive to seek out more power and provide better options for mid and endgame challenge content. This automatically adds to the survival aspect of the game.
3) Real dungeons. Stepping into a dungeon should more or less be like stepping foot on Eventide Island, which IMO was the greatest demostration of what BotW could have been with real dungeon design.
4) Make rain worth something more than just a grand annoyance
5) If you're going to make a game that's based around freedom, don't half-assedly try to shoehorn in characters that i'm supposed to feel some kind of connection towards. It does not work, I don't care about Zelda or any of the dead beast pilots because the game has given me no reason to. Link doesn't even talk about them or have any memories so it's not like he cares either.
That said, the Divine Beast story segments were easily the worst part of the game, there's something really jarring about playing this awesome free-roam experience and then having to YET AGAIN win over the hearts of some dumbass fish people or something when everyone in the story knows i'm the only one who's gonna get shit done and there's literally no benefit to anyone making me jump through hoops to do it. You're mad at me from 100 years ago? Who gives a fuck, are YOU going to save your village, no, alright then quit giving me the runaround.
Out of all of the Zelda tropes that BotW did away with, that was the one I wanted to see go the most.