Why you don't need a guide to 100% this game
|I have completed this game on my own without a guide after about 150 hours of playing. I've done everything except for the 900 korok seeds and upgrading every piece of armor to level 4. The armor upgrades aren't something I would've needed a guide for, it's just something you need to grind for, and I would've done it eventually if I had kept playing long enough to collect that many star fragments and other materials. The 900 korok seeds, well, doing that in the vanilla version of the game would definitely require a guide. However, the new DLC update that is coming out includes a Korok mask, which lets you sense nearby korok seeds in a similar way that the shiekah slate can sense shrines and compendium items. With this item, there's no reason why you should need a guide to find all 900 seeds.|
As for finding all the towers/shrines, great fairy fountains, and completing all the sidequests. You definitely don't need a guide to complete those things. If you think you do, you just haven't been playing the game properly and making use of all of the resources the game has available to you. What I'm seeing with a lot of streamers/let's players and other people commenting on their playthrough of this game, is they just keep underestimating how well this game guides you toward all of the areas of interest if you actually follow the most obvious paths, listen to all of the NPC hints, and look for contextual clues.
I've seen someone who had a lot of trouble finding the Gerudo Tower, because the Wasteland Tower is the one that opens up the the map of the desert, then they assumed the other tower was somewhere in the snowy Gerudo Highlands area, so they warped north of the desert and then went up to the Gerudo highlands searching for the tower for hours, not finding it at all... but actually, if you follow the linear path of bridges/walkways that you can clearly see from the Wasteland Tower area, you'll eventually get to the Gerudo Tower which is located in the little dip between the unmapped highlands region and the wasteland region, near the Yiga clan's hideout. This whole path is like the intended way for you to navigate your way from the Wasteland Tower to the Highlands Tower.
In fact, there's a whole bunch of those linear walkway paths all over the game, and if you stick to those obvious pathways that branch off from each other the game will intuitively lead you towards a bunch of things that you'd otherwise only come across on accident if you're lucky... hidden shrines or shrine quests, sidequest objectives, hidden treasures, great fairy fountains, and even a bunch of the korok puzzles are easily found if you stick to the main branching walkway/horse paths. Most people I see playing this never even acknowledge these linear paths that guide you toward all of these things, and instead they just climb and glide over everything and beeline towards that wherever they think they ought to go next. Sure you can look around from a high vantage point and get a general idea of where the areas of interest are, and mark them on your map, but you'll still miss out on a lot if you never restrict yourself to the main walking/horse paths.
And obviously, looking around at the scenery from various vantage points is very important too. If you haven't spent much time standing at the top of every tower/tall mountain, looking around surveying the scenery to search for suspicious locations you haven't been to yet, then you are nowhere near the point where you should be telling yourself "I need a guide to find everything". I've seen some people who just grab the tower map, look around for a couple seconds to spot a shrine or 2, and then they never return to that tower again even though there was a fairy fountain and several other things they could've spotted from that tower. Of course they didn't end up finding that fairy fountain until like 50 hours later by random chance...
I suppose the "Hero's path mode" that is coming with the DLC expansion will make it much easier to find everything, since you'll no longer have to keep track of where you have and haven't been to. So by exploring thoroughly and properly letting the game guide you towards the areas of interest, and by using this new feature to see where you've been, there is definitely NO EXCUSE to ever resort to using a guide to complete this game.