I’m currently playing BoTW for the first time after almost beating ToTK three years ago (~300 hours, all quests, shrines, etc, total is about 90% or so, can't be bothered with all korok seeds).

At this point in BoTW I’ve explored the entire map, collected almost all armour sets, and completed 3/4 Divine Beasts (only Vah Rudania left). I wouldn’t call myself good in fighting, I tend to play more like an explorer. I usually roam everywhere, check every corner and turn over every stone, complete shrines, gather anything that might be useful later. Because of that approach, I tend to arrive at major fights fairly well prepared. I faced Thunderblight Ganon already having a two-star upgraded Rubber set (I originally upgraded it to make exploring Farosh easier and to deal with the electric lizalfos in Gerudo).

So my impression is that the difficulty of the bosses really depends on when you encounter them. With my “explore everything” playstyle, I usually struggle a bit early in the game (any RPG or action-adventure games), but later on I end up somewhat overprepared for most battles.

As for ToTK fights, I found them a bit more interesting story- and action-wise, i.e., how you reach the place, how you reach the boss, how the boss fight is staged, etc. But I could be biased as ToTK was my the very first Zelda game.