It's not like this is going through a set order. There's been ADV Pokémon already, I don't see any harm.
Has no niche in OU that can't be filled by another Fire type with better results (Moltres for Fire Spinning, Ninetales for anti-leading) and thus should not be used.
I'm wondering how RBY Charizard should be played in OU. I know it sucks, but I'm trying to work out a gameplan. Is the idea to para/eliminate the faster counters, switch Zard into Eggy or Gengar (?? is there anything else Charizard would even be happy to double switch into? Jynx, maybe?) and try to set up from there? Charizard strikes me as a Pokémon that's very hard to switch in and that's very easy for other Pokémon to switch into, but maybe I'm underestimating Charizard's power/coverage?
Gen2
AFAIK it became relevant once the eeveelutions got access to growth, but unlike Vaporeon was not quite as good an abuser of the boost itself, thus it would (mainly) pass them around. Don't know too much else than Growth-Passing.
js, vap can pass growths around too, but unlike esp it can generally abuse them itself better