I'm starting to get the feeling that Charizard should be played a bit like Brawl Marth. His sucky priority means that he gets beat out by a lot of stuff up close, but keep them in range to get hit by a tilt, nair, or flamethrower and pressure them to death while simultaneously walling them out.
Charizard sucks in neutral, but you can circumnavigate that by sticking to the range that charizard works best at. Charizard does work up close, but I feel like we make the most of all of our options at mid-close range.
Ftilt has it's disjointedness, and it's a safe move to beat high-proirotiy areals like Ness Fair. Nair is... nair. Flamethrower is scary at mid-close range, you can toss it out against shield-happy opponents for some nice shield-pokage. You've got an awesome grab range and the speed to make use of it. Dtilt combos out of nair and potentially leads to gimps. Jab is a strong CQC move if and when you decide to move in.
With all the pressure you're applying, you don't have to work as hard to get reads. You can exploit your opponent's natural fight or flight response instead of trying to make MLG plays all the time. (Lets face it, smart rush down characters like shiek aren't going to give us the opportunity to punish them very often)
Resort to your usual jabs, Rocksmash, and grabs, and stuff if they penetrate your zone, charizard is good boxer so he can do that, go for more aggressive options once you start to gain momentum.
That's how I've been playing charizard lately, and it's been working out.
Now I just wait until someone tells me I'm dumb and that I have no clue what I'm talking about... then we'll finally get some discussion up in here <3