Truth be told, I actually think as people get better at the game, Peacock will be the one that scales most efficiently to the top.
This is super impossible to tell by any means.
Maybe people will actually learn how to approach against Peacock and she will become shit. Maybe Peacock players will actually learn that she is good at ranges closer than fullscreen and she will become the by far best character.
Maybe Painwheel players will find a way to properly use Unfly and Armor on top of her flight mobility to make her skyrocket on the tier list.
Maybe Parasoul players will learn that Tear Toss is actually kinda good - maybe someone will learn how to punish j.LP>j.HP on block and to just blow up j.HK Airtoss j.HK 30f gap pressure and her offence falls apart.
Maybe Double players will learn neutral game beyond j.HP. Maybe Double actually doesn't have a neutral game beyond j.HP, and she ends up as a char that gets snapped in relentlessly and then just dies because her defence is garbage.
Etc whatever
"I think that, when people get better, X happens" is pretty much just saying "I think that, when the game is played differently, X happens". And since these are unfounded random statements about a state of the game we currently have no idea about, X can literally be anything.
Maybe Japan was right all along and Parasoul actually has a 7-3 matchup against Peacock, with Valentine being a shitty character. Maybe not. Saying this doesn't really carry any weight.
She has a meterless reversal and generally an answer for most situations.
Peacocks main meterless reversal does not hit the air *at all*, gets LOW PROFILED, is throw vulnerable, and leads to Super. Her second meterless reversal option has 3f vuln startup, doesn't lead to anything, and is generally punishable even IF the opponent whiffs a move through your invinc frames. Her last reversal option is an invincible super that leads to absolutely nothing if you don't spend a 2nd bar, and is highly punishable if the opponent wasn't stuck in some attack.
Painwheels meterless reversal is actually an assortment of 8 different options, with varying startup vulnerability (on the ground as low as 3f, one air button with 2f), hitting relevant areas on the screen, and leading to full combos, but possibly losing to multihit attacks. Her other reversal options are a ground super that's postflash unblockable and has 14f invuln, one of the best air supers in the game, and a 2 bar invincible super that is not punishable at all and leads to obscene damage if it dodges an opponent's move.
Every character has "an answer for most situations", the question is how good that answer is.
Meanwhile, let's say for instance that PWs meter gain is designed to be bad. We now have a point character that can't build meter making her niche as a point character. You have to build an entire team around her and after choosing a second, your choices for a third are hyper limited. Is it possible? Clearly. But, no doubt this is best reflected in how unpopular she seems to be and her position at the bottom of almost every tier list I have seen.
Is PW a "niche" character that only functions with certain teammates? Yep.
Is that bad? ...Nope? Kinda the same is the case for Peacock, Valentine, Squigly, Eliza.
Which, btw, all aren't that popular.. aside from Peacock, as she's SUPER different from the rest of the cast, and a lot of people are willing to construct their team around Peacock, while a potential PW player might just go "Meh I'm happy with anything that can do fancy resets, if my PW team isn't that cool I'll play Filia instead".
More to the point, meter gain shouldn't be one of those things that greatly differentiates one character from another (I'm okay with some variations on meter gain, of course). This is because it is usable by the whole team so meter gain on a point character affects every other character on the team meaning that a Double sitting behind a Peacock is going to auto-magically be better than a Double sitting behind a Painwheel.
Most things affect a whole team.
A BigBand sitting on anchor is going to auto-magically make your point and second better than a Valentine would.
A 2nd position Filia is going to make your Peacock's defence and midrange poking SO MUCH scarier thanks to Mp.Bang xx Argus xx Gregor that people have to play an entirely different game against her compared to a Parasoul 2nd.
A Bella 3rd changes your Parasoul when cornered from "Dead" to "Hi, I have a Reversal that will randomly cross you up and put you in the corner in a hard knockdown state with Bella in your face", which forces the opponent to play tremendously more careful, which in turn gives your Parasoul the space she needs to play her game from a disadvantageous position
Etc
Yeah, high metergain on your point is cool, but constructing your team around your point building a ton of meter also makes you susceptible to lose the game on the spot if your gameplan gets disrupted (eg Double gets snapped in).
Painwheel isn't really optimal on any position (too low metergain for point, too bad assists for not-point), however at the same time she is also not SUBoptimal on any position. Anchor PW is still a character with one of the best DHCs in the game, and installed PW doesn't really require assists to help her in movement/defence/whatever.
