If you want a history lesson then A link to the past is undoubtedly the game to play. Ocarina of time, like most early 3D games, is very much a "you had to be there to truly appreciate it" moment in time.
Breath of the Wild isn't a better game, it's a completely different game. It's not even a later stage in the evolution of the Zelda formula, it's way out of left field. The (arguably) best Zelda 1 speedrunner in the world, LackAttack24 [1] even goes so far as to call it "NOT a Zelda game".
Personally, I am not a fan of modern open world games in general. I feel like they trade off quantity over quality in the most extreme way possible. On the other hand, the tight, cohesive feel of a classic Zelda game is absolutely sublime and an experience that is often imitated but never duplicated.
For 2D games the one to start with is A Link to the Past. It solidified the franchise formula of combat, exploration, and puzzles that started with the first 2 NES games, both of which were experimental games at the time.