I first got oot along with my n64 the Christmas following the release when I was a kid. The cool thing about the n64 was being able to play nintendo classics in 3D for the first time. As a Zelda fan, having grown up with the nes, gb and snes versions, the new perspective of the game was enough in itself to keep it entertaining even in its slower moments, like prior to opening the door of time in the beginning and some of the slower dungeons like lake hylia.
I think since we have much better consoles these days, that effect is kinda taken away. Most people that still see this as a cornerstone in the series got to experience it at its highest moment as a revolutionary platform.
The slow buildup in the beginning is pretty common to the other zelda games during that time, and they tried to port the fundamentals to the 3D environment. Over the years as consoles, as well as the series, evolved, the game became more adapted to newer platforms. Oot has a long intro process and 3 small dungens/tasks to be completed before the game really takes off. Alttp is identical in this way with having to collect 3 pendants before really gaining freeroam.
Gameplay aside, the story is remarkable and some would say the best so far. if you're a fan of the series, this game is as important as people say. You just have to acknowledge that youre playing a game from a time when they were porting 2d games to 3d. Things will be clunky, and gameplay slow paced in periods. Just keep an open mind.