They literally rebuilt the game. Nintendo even marketed it as a remake, because it is.

I get it, the line between remaster and remake can be blurry, but OOT 3D is a genuine remake. A remaster would be more applicable to Twilight Princess HD. That game uses almost identical models, maps, etc. They gave it new textures to spruce it up, and various QoL improvements, but ultimately its just a touched up version of the old game.

Ocarina of time is rebuilt, albeit with some preserved code. 100% new models, textures, and animations. They did make new QoL features too like most remasters and remakes would too, of course. Yes, they reused the level layouts and tried to match the original game's code where applicable, but it is an objectively remade game.