[Game Developer breakdown]) while the goal of the game (save Zelda) has not changed in all these years, the mechanics that nintendo wanted to implement have drastically changed, from becoming an RPG, to a platformer, to a combat game, to sandbox, Zelda's evolution is something I guarantee has allowed audiences to stay invested in the series.
Despite Zelda's target demographic of young gamers, it has managed to keep its core audience that it has built so long ago, here is an image of their latest title, while it was released for a younger audience, even I had fun creating things in it, Nintendo has truely kept its longevity with this title. 