G&W Got a new FAir, a bomb toss move. At first glance this might seem like a cool upgrade, but compared to the box flip FAir of old it's just abysmal. It has a ton of startup AND endlag, while it can kill (at high percents, keep in mind) any character with moderate speed can get out of the way even if right on top of it. It doesn't really combo or confirm well into anything from my labbing of him, either. On top of that, just the usual G&W problems. He has one of if not THE worst roll in the entire game, it feels like what some other characters have after 5-6+ rolls resulting in tons of frame lag being added to their roll due to how they work in Ult.. and that's how his roll feels fresh. Once it picks up ANY lag, it's almost painful to use and isn't ever a good idea.. it's EXTREMELY punishable.
Speaking of punishable stuff, everything about him just about is. His NAir (the fish bowl thing) has a decent hitbox but doesn't do the kind of damage nor have the kind of knockback to translate into anything. His BAir leaves him totally helpless in the event the move doesn't connect. His UAir is.. okay I suppose. DAir is probably his best aerial, which isn't saying much because I'm not a huge fan of moves that quickly snap you down to the ground like the DAir key slam does. He has no synergy to his kit at all, he feels extremely laggy and clunky.. he kind of reminds me of a worse melee G&W. Only now instead of a lack of L-Cancelled aerials or a messed up shield, it's other serious problems. I could go on for hours about how messed up Ult G&W feels. He used to be my go-to bad character, but now he's so crap I can't even use him as a joke.
Mac had a number of things done to him going into Ultimate that just didn't do him a single favor. The recovery 'buff' affected him more like a nerf, when knocked about in the air he doesn't get his side B back, his aerials are all crap and he's lost his infinite, DTilt combo is gone, neutral B is one of the worst in the game and I really wish it could've been a star punch move.. oh Mac. He's a free kill any time you get him offstage, terrible recovery aside he has NOTHING to defend himself with properly in the air and gimping him when he's in recovery distance is extremely easy. Otherwise you can just watch him awkwardly fall to his death if hit far enough out most of the time.
He has pros of having powerful armored attacks on the ground and being fast, and his cons include.. literally everything else about him as a character. His fundamental design just isn't favored by a game like Ultimate. Maybe in a FFA or 2 v 2 he could be higher up in the tiers, but for 1 v 1 fights he's totally out unless you simply like him as a character or want to be disrespectful. There's no reason to pick him or G&W over ANY other character as any time invested in them would be infinitely better spent in other characters, even low tiers. Charizard is just, bad as I've mentioned above, no reason to ever switch to him really as PT.