AA you don't give Charizard enough credit. Charizard has one of the best out-of-shield games in the entire cast. He can punish from any angle you could hit his shield at (except for directly below him, i guess) with quick, powerful moves with range. Combine this with Flamethrower, a terrific zoning move, and Rock Smash and you have a character with very good defensive tools. Rock Smash is just awe inspiring when used correctly, there are SO many opportunities to use this move when you have good reading and good reaction time (something as simple as a MK dash attack is an example of a move that = 30-40% and death at 110% when you combine the two qualities). Charizard clearly has his flaws, like exploitable blindspots and terrible, terrible get up options. But when you are capable of punishing so many moves and dealing so much damage in such a short time span, Charizard becomes a decent character with good, not great, matchups across the board, with his worst matchups being those against characters that can projectile camp him hard and take advantage of his terrible get up (Falco, Dedede, Snake).
By the way, Snake still ***** PT hard. All Ivysaur really got in this matchup was a more powerful dair, which is helpful for cyphers, and a more powerful bair, which is nice but Snake's tilts are just so powerful and quick that it's really not something Ivysaur can heavily rely on in this matchup since it's not as safe as it needs to be for Ivysaur to succeed. Ivysaur's spacing game just doesn't compare in the long run, particularly when you compare the two characters' tilts. Add to this the fact that Ivysaur is a terrible KOer, Snake is incredibly good at protecting himself from the few KO moves Ivy does have, and that Snake is ridiculously heavy...oh, and the fact that Charizard is absolutely destroyed by Snake doesn't help much. Squirtle is okay but Snake's absurd combination of speed and power mean that Squirtle's going to be dying quite early. Which is really bad when you consider that Squirtle is the Pokemon you want to use the most.