As iconic as Ash's Charizard is, it hasn't really done anything of note since the Battle Frontier arc, where it jobbed hard against Brandon's Dusclops. Squirtle took out Ninjask, Bulbasaur took out both Dusclops and Solrock, and Pikachu took out Regice, making the Charizard the only one not to get a single win in that battle.
Nowadays, if they want to shill Charizard, they use another character for it, such as Alain, Kiawe, and Leon. The days of Charizard being Ash's strongest Pokemon are long gone.