Erm... Little mac? You mean the guy who cries whenever we drop a trampoline in front of him?
Or hell, tier complaints three weeks into a game release? Are you serious? Outside of probably Diddy Kong, I don't know if anyone even knows what the "top tiers" actually look like.
If he wants to go play Diddy or the top tiers on his own, he can go ahead. But we're in the first months of a new fighting game. No one knows how to do any real advanced tech yet. In particular, perfect pivoting has only recently begun to be used in tournaments, and I've never seen a PacMan do theoretically useful moves like Wavebouncing / B-Reversals to control spacing while charging a fruit (like Robin / Lucario players)
Or hell, I don't think I see Pacman on streams / tournaments at all. There really isn't much footage of him.
He feels that pacman can't keep up with the current meta game and that's he's going to be D tier.
Maybe he will, maybe he won't. Welcome to new fighting games: no one knows anything.
So just play the game the way you feel like it. In a few months, the meta will begin to stabilize and we can start discussing "issues vs top tiers" at that point.