Uhhhh, Fox's Upair comes out frame 8, and Bair comes out frame 4. I don't know what you're talking about. They are also way easier to hit with than Ness's Bair, which he has to sweetspot and doesn't have much range.
The frame 8 hitbox on uair doesn't KO and can be SDI'd, making the frame 11 KO hitbox just as hard to hit with consistently as Ness's bair, if not harder. Neither Peach's bair or nair have near the KO capacity as Ness's bair. They're edgeguard set-ups.
As far as what I see wrong with Lucas, he used to have trouble approaching, comboing and KOing. But, he's fast on the ground, with a pretty quick projectile, giving him decent oki, and he has one of the best edgeguards in the game, meaning he doesn't really need combos or KOs anyway. But he doesn't have good zoning, or a good way to close the gap. The fixes made were thus: make PK Freeze land cancelable, and allow Lucas to retain his forward momentum during it. Grounded PK Freeze fires upward at about a thirty degree angle. PSI magnet now causes Lucas to advance forward very quickly, eating through any energy projectile in his path, and ending in an attack with buffed damage and knockback. Jab has more range, uair has a high base knockback, and a low knockback growth.
There's no direction to these buffs. The PK Freeze buffs apply to a zoning character, which I've already established that Lucas is not. He can use aerial PK Freeze to create approach openings, but it works better when used in tandem with grounded PK freeze to control both the ground and the air to force the opponent to try to force his way through it by attacking blindly. Psi Magnet was just absurd, and made no sense as a move. To my knowledge, it still hasn't been reverted, which is just silly. The uair sought to make Lucas combo better. Dair was also changed, although all it did was remove a pressure mix-up.
I realized this character was broken after G6, when Twitch started messing around with Lucas, and the only way other characters could even fight him was to bust through PK freeze with an aerial at full speed, and surrender all of the positioning and game time that that takes up. All it took was setting up a good spacing, and you could punish any character's approach. After that, you just combo the hell out of them, then knock them offstage, and edgeguard with PK Thunder. This character was perfect, and that's not a good thing. A month later, a Lucas trashed everyone at some PMBR tournament, presumably using a similar strategy to this, albeit even more nuanced.
So a couple nerfs were added. Lucas's PK Thunder 1 was shortened to pretty much only make it useful for recovering, but PKT2 was also shortened, so it wasn't even really worth it to use that, making rope snake the only viable recovery Lucas had. So to recap, we now have a character that has ridiculous onstage space control, incredible pressure, and protracted, damaging combos. The only problem now is that he can't KO or edgeguard, and he can't recover.
So now a buff is given to solve the KO problem. A new bair. It does absurd damage (therefore absurd blockstun), absurd knockback, and has absurd range. I shouldn't have to break down why this move is just... nonsensical. Just watch any stream with Lucas. He's spammy, lacks nuance, and just doesn't really change his gameplan up much. Most of it is PK Freeze and bair, with a couple uair combos thrown in.
For some context, I spent a lot of time with Lucas around the time Demo 1 came out. I recognized that he wasn't up to par, but I felt that with some dedication, a game plan could at least be figured out. And I figured out some really, really cool things. Fair was an incredible poke, that could be thrown into block strings safely. It also combo'd if DI'd incorrectly. PSI Magnet and ftilt could semi-spike, setting up for really easy edgeguards. Dair could be mixed into pressure strings to punish jumping out of shield. PK Thunder 1 was one of the safest edgeguards in the game. Most importantly, nair chewed through spot dodges, and had short enough cooldown that Lucas could follow rolls with mix-ups afterwards. I found a lot of really neat ways to pressure opponents once I got them locked down. The only problem was that locking them down usually required a pretty egregious error on their part. But then I looked at Lucas's hitboxes and realized why: nair's hitbox doesn't even cover up his limbs. The reason he gets swatted out of so many jump-ins is because he's totally exposed in his only good jump-in move. Around this time, Yeroc asked me for a write-up on Lucas. I gave him two answers. One of them, I'm not so fond of, to the point where I don't think it bears repeating. The one I'm most fond of is this: Make nair bigger.
That's it. That's all Lucas needs, and he retains all of the really neat, nuanced, natural-feeling and really unique options that he had to begin with. Now, though, Lucas has been turned into some kind of Frankenstein's Monster of a character. Changes are made aimlessly, as if the people in charge of the character are just throwing darts at a bunch of post-it notes, and hoping this causes the character to cohere into something meaningful. Why does Lucas now have Guile's Flash Kick? I really wish I knew. All I can say is, Lucas was really cool in Demo 1, and could have had a lot of potential with one tweak. Now he's not cool, and I don't even want to think about his potential.
