Throwing the issue right back at you, every time, you seem to ignore everything that's been mentioned and consider it as raw data, rather than tools that make the character versatile in one way or another.
I'll mention it once again, but Doc's Bair autocancelling is truly one of the best assets about it, and what sets it apart from Kirby's. The ability to throw it out of a SH FF, rather than just a SH. The ability to just throw the move at any given time is truly something to marvel at and one of the stronger points of Doc's neutral game. And as i've said, to take back your example of Cloud's Bair, Doc's SH AD or even FH AD options are among the best out there, so while you're not beating it, you definitely are not optionless. Kirby on the other hand, with his even worse air speed ( despite better air acceleration ) and a Back Air that fits more into the area of raw moves rather than combo starter potential moves like Doc, limit his potential at actually beating the move. It isn't even his only option out of airdodge, as we've mentioned right before.
On to advantage, i wholeheartedly disagree that Doc's moves do not allow him to accomplish about as much as Kirby does, especially on anyone but fastfallers. Doc has a ton of bread & butters combos that can come from various starters such as his Jab, Down & UpTilt, or Grab. Some of them are rather frame tight but they allow Doc to get about 25% out of every one of these neutral victories, regardless of the character. Kirby on the other hand, especially against floaties & the likes of Luigi, won't reach that kind of consistency beyond Mid %. That isn't even mentioning just how much better Doc is at killing than Kirby, whether it's his kill confirm & 50/50s, his strong smashes that also are on the lesser commital side of things ( Yes, even FSmash ) , and his absolutely ridiculous out of shield game. With this taken into account, i'd actually give the edge to Doc when it comes to the advantage state against a couple of characters.
Finally, back into disadvantage, while it is true that Kirby has the air acceleration to shift his momentum around & trick his opponents, his air speed however remains one of the worst, and along with his floatiness & lack of fast options in the air, he will still have a hard time getting off of the face of his opponent, especially when we consider that nearly every character that is praised for their juggling prowess has a better air speed than Kirby. When put into perspective, these tools don't value much. Same argument can be made for Recovery, his UpB is kind of bad on top of that, so while his multiple jumps offer him the mixup of recovering up, this will hardly matter against the likes of Cloud.
So yeah, i'm kind of sorry, but i'm not seeing it either. I do know that Kirby's ground mobility is decent enough, I do know that Kirby has good combos against fastfaller, I do know this, I do know that, but i can't really visualize how any of these tools will actually make Kirby win anything besides a few matchups that renders him okay enough, while losing the majority of matchups out there. Maybe with some footage, i could understand what's so nice about Kirby, but as of now, consider me unconvinced.
No, I hear what you're saying. But it all sounds like defending Doc as a character - and he does have very good tools. The issue is that nothing he has really puts him over Kirby. I'll take care to respond point-by-point here.
For the first paragraph: Doc's autocancel is great, for sure. But Kirby's is meant to have a couple different uses. First, when thrown out from a SH, it's a faster option than Doc's. Even moreso when you consider how air acceleration improves SH game. It becomes a burst option you can indeed throw out. Second, you want to land with the move more often than not, as despite the landing lag, it's meant to pancake under moves, increasing safety and the ability to avoid moves. Doc's bair is still stronger, mind. But it's not so much stronger that their bairs are incomparable. And on that note, Kirby also has a really good sh airdodge and fh airdodge. But the issue I think we're ignoring is that you shouldn't rely on aerial approaches so frequently anyways, especially with poor airspeed and acceleration. You see, that's why Doc's momentum shifting also doesn't matter so much. When he reverses his momentum, he can't do much afterwards. Kirby can punish a commitment from above right afterwards.
Second paragraph: Advantage state includes combos, but isn't just about combos. Without even getting into frame tight combos, Kirby can do 30% easily, and upwards of 70% depending on the opponent. But again, not just about combos.
Kirby is also stronger at ledge, due to his jab acting like a slightly worse version of Falcon's. It's not too hard to react to a number of ledge options just from holding it.
Kirby is also stronger offstage, due to the ability to chase opponents incredibly deep without significant threat to himself. He can place his aerials pretty much anywhere as a result, as opposed to a particular spot.
Finally, Kirby is also stronger when an opponent is landing. Due to (again), the better ground game and speed, he is able to more effectively chase the landings of his opponents. His turnaround speed is actually among the quickest in the game, allowing him to shift directions pretty easily, and his utilt annd usmash are effective anti-air options. The latter move is slower, but has incredible vertical range.
As for killing, Doc mainly performs better due to his kill confirm and usmash. I acknowledge both tools are solid (especially usmash), but the angle of usmash often keeps it from being as solid as the other Mario brothers. Furthermore, his kill confirm isn't as effective with enough rage. On the other hand, Kirby has more situations in which he can secure a kill, due to having more neutral tools on the ground, better edgeguarding and a vertical kill throw. I see Doc like Zelda in this regard - yes, there is a powerful kill confirm. But it's typically not going to be as effective due to opponents being able to outstrip him in neutral. That said, I will give him a solid edge in kill power.
Taken together, these attributes make Kirby stronger in every state of advantage. Comparatively, Doc may perform better if he's chasing an opponent in the air, due to slightly better airspeed and quick uairs. He will also perform better if he's able to get the grab he needs for his confirm.
Finally, disadvantage. Regardless of the airspeed of many of his opponents, Kirby is able to escape pressure and return to ledge more easily than most characters. Getting to land back on stage is no easy task, but few characters enjoy the privilege of being able to jump away from Rosalina's uairs instead of jumping out of them. Or jumping out of Fox's vortexes. So on. Airspeed only matters so much here, as ultimately, most characters have just one extra jump. After that's exhausted, they need to land before putting on more pressure. This inhibits their ability to chase Kirby down fully.
A similar point is applicable offstage. As Kirby can pull back offstage, he is able to force the opponent to exhaust their ability to chase. With this window of opportunity, Kirby is able to make it back to stage. He can also simply choose to recover high (or low if really needed). His up b isn't good at all - I'll be the first to call it trash. But if that's your main thought when it comes to Kirby's recovery, it's not the right direction.
So with these responses, I believe that should explain everything. You have agreed that Kirby has a better ground game, however slight. Disadvantage is clearly in Kirby's favor, with little room for comparison, I think. Advantage is also solidly proven. The only areas I believe you could reasonably argue for are the following:
- Whether Kirby's superior ground game is enough to say he has a superior neutral
- Whether Doc's kill power alone makes his advantage better than Kirby's
I believe that's a "yes" and "no" respectively. Again, all of this is before getting into MU specific copy abilities, which can objectively put his neutral, advantage, and disadvantage leagues ahead of Doc's depending on the MU.
EDIT: And before I forget, I want to reiterate that Kirby has better top-level results than Doc as well (despite both being admittedly tragic). So this covers both theory and reality.