Charizard may have more Special Attack than Attack but it just rules in the Physical Sweeper department. Fire Blast is stuck on the Physical Sweeper Moveset because it gets STAB and has Blaze Trait making it more powerful when it's weak. Don't forgot those Physical Tanks that'll try and stop you so you need a Special Attack in there too.

Charizard@Liechi Berry/Salac Berry
Fire Blast
Rock Slide
Earthquake
Swords Dance/Dragon Dance