It is true that the second generation of Pokémon has a terrible experience curve, as well as a huge imbalance in power and types between Pokémon.
That said, this game's journey is one of the best in the franchise. Being able to choose between a boy or a girl for the first time, you explore Johto, an area based in Japan, with events occurring shortly after the Kanto adventure, where the Rocket team tries to rise again after Giovani's disappearance, faces a new Elite Four and discovers that you must go to the continent of Kanto, challenging all the old gym leaders, following in Red's footsteps to finally challenge him!
This approach, unfortunately, was never repeated by Game Freak, and is a masterclass about how to make a sequel.