I see nothing wrong in utilizing a boss battle with the kind of gameplay you're capable of, ie using your weapon of choice and item to beat the boss. Mostly, it is a battle to find weakspots as well as aiming towards them. It is not a simple "Smash the f*cker until it is dead!", you have to actively find out how to damage the boss in the first place.
I am a fan of bosses being clearly portrayed as
bosses - powerful rare enemies being more unique than the average foes. Metroid did it great, Zelda as well... until Breath of the Wild.
Nowadays I see bosses of many games and I am just seriously bored. It is always the same boring and repetitive hack & slay ****. I'd rather see hundreds of traditional Zelda bosses formular battles instead of one more of the aforementioned bosses. Well, at least in most games, it doesn't require that much of equipment to beat most of those hack&slay bosses, so they're kinda save. But BotW? Hell, the overworld is
your playfield of pure experiments of gameplay elements, items and much more supported by the physics engine... Making up one or two gigantic dungeon bosses in which you have to use your actual surroundings and the physics engine, ie throwing rocks with the stasis towards a boss to weaken their defence or some similar stuff, would already be a fine start!
Furthermore, your argument "They should be more of a challenge" can be easily implemented with the traditional Zelda formular as well. Just make the weakspots more tricky, give the boss more HP, make it deal more damage and more unpredictable moves, bring up more weapon varieties as well as the use of specific item
s - there you have your challenge. A Link to the Past, again, was quite close to it. I knew the weakspot of Helmaroc King, yet it didn't stop the boss to whoop my ass several times.
Arrows + weapon of choice - that's how I beat them mostly.
Due to them being very boring I tried finding out ways to beat them differently; it didn't change my viewpoint that much since Ganon Ganon was still annoyingly boring.
That's actually a mechanism to stun the boss
without aiming towards their weakspot whilst giving Ganon Ganon the hack&slay experience.
They clearly regressed this stun formular what you've been criticizing so far.
You know, there were some gameplay mechanism of bosses being weak to arrows... which made the use of the bow against them quite satisfying - until BotW brought up 4 Ganon Ganons with the same mechanism. They are just as bad as the bland Divine Beasts, no love but copy & paste.
I might be really harsh on some core elements of BotW but it is necessary. I view them as huge weaknesses of the new Zelda formular and it needs to be addressed and changed. As I said, it is a clear regression in terms of bosses, especially since they're not even in common with the more unique gameplay mechanism of BotW itself. I loved Zelda bosses because they were so well tied to the physics engine, level design as well as the gameplay. When you battled one boss, you clearly felt the impact of said boss how it is connected to the game, figuratively.
I partially agree, they need to be more tricky but not exactly as similar as those bosses in Dark Souls: bring up more roots from the traditional Zelda bosses while looking out for some gameplay varieties from Metroid bosses or maybe other ones, as long as they stop doing the old hack & slay boss battles, I'm fine with either options.
Also, again, I can just highlight the possibility of the creative use of items here again. You can use items as well to open up the defences, I don't see the issues in here - as long as the boss battle feels creative again... Once again, it works with SoulsBorne games perfectly fine and it is alright since it fits to the gameplay mechanics but Zelda games are still built different (not in terms of quality btw). You can't just demonstrate the players a vast world with very interesting physics engine + gameplay and then throwing it away for the most uninteresting, repetitive and bland looking bosses in the history of Zelda games. Ironically, the DLC boss was a very cool boss - because it was required to use a high amount of the gameplay elements against him; and the monk was just a humanoid boss. Imagine bosses like Gohma, plant based bosses, dragons and other creatures.
VS
Glowing eyeball, glowing eyeball, glowing eyeball, and glowing eyeball + Ganon Ganon, Ganon Ganon, Ganon Ganon and... Ganon Ganon? Another regression!
Hell, even Age of Calamity - a Zelda Warriors game! - brought a more individual design to them:
Man, I can just hysterically cry and laugh about this one, the designs are actually so bad, a Warrior's game surpassed them. Please Nintendo, my heart cannot bear one more of the Ganon Ganon guys in BotW2 anymore.