The Fire and Shadow Temples are both fairly interesting and have fun moments but like all Zelda dungeons involve a few puzzle tricks that revolve around the main items you just collected. I liked the Shadow Temples hook in that you needed to use the lens of truth to detect hidden doors and platforms but by the end felt it was a smidge overused. Which leads to my biggest critique of Ocarina of Time.
Ocarina of Time repeats itself too much. Once Ocarina of Time gives you a new item or some new mechanic then it proceeds to overuse it. I don't mind coming back to familiar mechanics as that's the base for really great games but in the case of Ocarina it's feeling very samey to the point of being tedious in the late game. Inserting longer and longer dungeons could be interesting but I find Ocarina of Time has many of the same pitfalls that other games have. Which is one of the reasons I rate the older 2D Zelda games so highly, they are shorter and more focused experiences. That said, Ocarina of Time is a child of it's time and Nintendo worked some absolute magic to make this game as great as it is with the limitations of the Nintendo 64. In some ways modern critiques of Ocarina of Time are like saying Citizen Kane is a bad movie because it's shot in black and white the 1.33:1 aspect ratio. Citizen Kane is an absolutely incredible film and a product of it's time and limitations while remaining a fantastic film.
To be honest I never completed Ocarina of Time when I played it on the 64 back in the 90's. I always bailed at the same place, The Gerudo Fortress. To me the game started getting tedious at that point and I just wanted to do something else. Recently I just got to the Gerudo Fortress and apparently I still feel similarly. The only difference is now I want to finally complete it so I hope the game picks up a bit of steam here. I'll admit i've come to this point with many games, Borderlands 2 being an example. Borderlands 2 is a great game but like Ocarina I felt the content was stretched to be too long for my taste. A 15-20 hours long Borderlands 2 would have been absolutely perfect for me but it needs to exist in a world with a much longer playtime to meet modern players expectations.
All that said, overall i've quite enjoyed the game despite some of it's flaws and am really curious to see how the game ends. And, i'm not sure why, but the thought of fighting Ganon in this game is daunting to me. I've always felt like the Ganon portrayed in Ocarina has always been more sinister than other Zeldas as he is a character that shows up now and then and always seemed creepy to me. I think this is the games limitations at work because Ganon never actually emotes so my mind fills in the gaps which is somehow more sinister than he would otherwise be. It's like reading something from a great book where your mind has to fill in the gaps which can make it more personal and immersive.