I've heard Kid complained about quite a lot myself, and most top players are placing him in the same tier as Cell/AG/16. Even if you take the stance t.s not in that elite tier, I don't see how you can argue that he's not rriighht outside of it.. which would mean nerfing that tier would likely leave him far too strong in comparison to the cast.. but I don't think he's right outside that tier, I think he's in that tier and close to the top of it.
The issue isn't that Kid has one OP thing that defines his strength, and I think this is tied to why he isn't AS complained about. AG has his block pressure and mix, 16 has the the HKD stuff, Cell has the neutral and insane damage, and so on. You can look.at these characters and say "yeah that thing right there is insane".. with Kid, aside from his blockstun mix (tied for best in the game, if not THE best), it's a matter of him being a jack of all trades and master of every one of them.
Kid's assist is one of the best in the game right now, though definitely harder to set up and use properly than some.
Kid's neutral is absolute bonkers. His j/5m is simple insane and is the embodiment of control. His 2M is one of the best normals in the game, hands down.. And it let's him play neutral from 80% of the screen off an un-seeably fast, low with no risk tied to it outside using it improperly.. and if it lands, from anywhere, it converts big. Unseeable, safe, fast, almost full screen low that's easy to confirm and requires no commitment to do so, regardless of distance, and at distance, can simply be chained into itself, leading in to a combo that for a bar or an assist, does an easy 40% on the low end, with the option to take it higher as you see fit. His 2L is nothing Earth shattering, but a fast, machinegun low should never be underestimated. His j.H is.quite good..his 2H isn't great in general but from the right angle is quite strong. His 5/2S stuff is useable in neutral due to the way it works, allowing him access to air options very quickly during neutral play.
Kid can bang in a fireball war as well, with his Candy Beam and actual beam, both being amazing. His air beam has no height restrictions, so you can use it as a grounded beam as well if you want to - and there are solid reasons to do so. Candy Beam heals as well, which isn't huge but in a fireball war that kinda health swing can make a trading a little back and forth highl favor Kid. His regular ki blasts are better than they might seem.
He has a command grab that covers a large amount of screen space, and can make approaching him dangerous. Now, right now this isn't as relevant, because even though.Kid can play back some, there's just no reason to want to.. but if the game sees changes to pressure, and other playstyles become more viable, this option is going to stand out as a large strength. The right assists allow meterless conversions off the very fast L version, or burn a bar on H.amd follow up yourself off althe very fast H version.
Kid can mix like a Cuisinart and his blockstring pressure is very powerful, especially with 5SS and 2S allowing air options the way they do.
Ball pressure to end combos.
Tiny hurtbox.
Kid's air control is excellent as well. His ki blasts arresting, but partially retaining momentum makes him very hard to pin down in the air, with ball to just fuck off outa there if he wants, and his j.m letting him do some weird shit, like escape in odd situations, or even engage while backing up.
Etc.
Kid is very very very good absolutely everywhere.
As to what I think needs to be changed, that depends on what's changed with the game universally and with other characters. I very very much want him to keep his neutral and his pressure, so perhaps toning down his mix in some way, or tone down his pressure in some way and keep the neutral and mix. I hope we don't see it, but I partially expect a damage scaling nerf when multiple 2M are used. So if I 36M 2m 2m into a combo, i could see that not doing almost half your life. I don't know what's optimal here,but I've gotten 4400~ for a bar and about the same for an assist. I don't know if a character that does all of that should also have the assist he has. I hope he keeps the version he has now for himself, it's tricky and requires resources to set up - if they weaken his mix in some way.i especially hope he keeps it.. but when it's used as an assist, it might be too much.
I'm just spitballing here with vague ideas because we don't know what system changes there will be.
If we see blockstring/assist mix really weakened universally, then I can see Kid skating out almost entirely intact.. but he will still be on of the best characters in the game, simply because he can play anyway he wants, any range and any style, and he's never at a disadvantage.