It's not easy mode, it's "not annoying mode." And you have yet to tell me WHY it's integral to dungeons and why it makes dungeons more difficult. "YOU HAVE TO DO IT FASSTTTERRR!!!!" isn't an excuse
It's easy mode whether you like it or not. Having to do something faster is adding another layer of difficulty. Making a work of art is much easier if you have 20 years to do it instead of 5 minutes.
Now, why is it integral? Simple, the dungeons are designed around to be beaten in the 3 day time limit. Even if you're slow they even give you a "checkpoint" if you are too slow when you get the relevent dungeon item. You can essentially wind back time in the dungeons once you get the relevent arrow and return to exactly where you were. EG, stone Tower temple, you get the light arrow, you can instantly flip the dungeon over if you go back in time and essentially nothing has been lost other than fairies.
Majora's mask Is ALL about time management. "Should I go for the fairies now or try and finish up the quest for the postman's hat?" Having to choose between sidequests and dungeon exploration is an integral part to what makes Majora's mask enjoyable for many.
As someone who loves the game and has beaten it many times, yes, it is for me.
But turning off the time limit in dungeons wouldn't do ANYTHING in changing the fundamental basis for the game. As it's not fundemental or important to the dungeons at all outside of adding an annoying element to it.
Wrong, having to manage your time is part of the game's difficulty, design and appeal to many. Not for you? Maybe you'll get easy mode.
Again, the dungeons are all designed with your time constraints in mind. Part of the challenge is doing things in a lower time, but MM is pretty damn forgiving, especially if you know the reverse song of time and reset time before entering a dungeon (IE have good time management)