Strong Pokémon. Weak Pokémon. That is only the selfish perception of people. Truly skilled trainers should try to win with their favorites.
Otherwise you're forced to level up a lot more, and that just becomes a chore easily when you're doing the main game story...
I mean, Druddigon is terribly slow, Cinccino has horrible defenses, and Swanna is mostly kept around as death fodder and HM slave. But I liked them, and I used them.
Magnezone really is the only competitive Pokémon there... OTOH both Lucario and Arcanine are strong competitive Pokémon with high BSTs. Nothing wrong in liking them (I like them too), but hey, don't judge!