Melee Falco was defined by being very combo-heavy, vertically-inclined with setups and kills, a quick and powerful spike, and having a broken projectile while Brawl Falco was more defined by a broken projectile, chain-grabbing, quick and powerful spike, and poor kill options. Smash 4 Falco is kind of a mess of a character who is combo-heavy, but lacks true combos past low-mid to mid-percents, is more vertically-inclined like his Melee incarnation, and was found to have a strong edgeguard game due to how his Fair works, how his Nair works after patch 1.0.8, and how his hitstun interacts with ledge grabbing allow him to abuse Blaster's set knockback. Notice something missing? Yeah, his projectile game is lacking if not nonexistent for practical purposes.
The whole, "Falco was a broken monster" wasn't his fault, but the developers. Melee Falco was wacky, but they decided it was a good idea to make Brawl Falco even wackier. They gave him a faster firing, farther traveling, faster laser traveling, and entire screen covering Blaster, gave him and Fox intangibility frames on their Phantasm and Illusion, but to top it off, Falco's went from frame 18-19 to 16 - it became even faster -, still allowed him to keep a frame 5 Dair without weakening its power to compensate for its speed, and somehow allowed chain-grabs to exist in Brawl. Sure, he lost a frame 1 Reflector to setup and hit confirm, but he went from a massive comboer to an annoying pest of a character who locked people down with the most broken projectile in Smash history.
So, what did they do? Questionably, they made his jab worse for no reason - it wasn't abusive and it wasn't anything close to Smash 4 Fox's pre-patch 1.1.0 jab -, they doubled dash attack startup while leaving Fox's alone, added 1 frame of startup to Side Smash for ***** and giggles, increased Dair's startup by 11 frames, thus, homogenizing it with Brawl Wolf's Dair, Captain Falcon, Ganondorf, Ike, and Smash 4 Roy's Dair, increased standing grab's startup by 2 frames, 6 to 8, when his Melee standing grab startup of 7 would have been fine, halved Falco Phantasm's hitbox, never did anything to Fire Bird to make it anything than strictly an inferior version of Fire Fox that unreliably multi-hits and travels less while having the same startup, and removed Blaster's auto-cancel windows without compensating for any of its end lag kept from Melee and Brawl. The only good things nerfed about Falco was removing the intangible frames of Falco Phantasm to make it less of a get out of jail free card, but halving the hitbox borders extreme when it makes his recover that less safe even compared to Little Mac and the removal of Blaster's auto-cancel which can stop it from being a quick, spammable projectile, but leaving its massive end lag is a major issue. The other nerf: removal of chain-grabs was a universal change, so nothing can be said about that strictly towards Falco.
The only buffs he received by launch was that rapid jab gained a finisher, Bair became stronger, Up Smash gained 4 active frames and does 6% more in return for 5 more total frames, and Fair links better, gained a finishing hit and landing hitbox, and had 1 less frame of landing lag. After patches, his Up Smash linked better with the second hit gaining some active frames - I can't remember how much -, Nair gained auto-link angles to link better, Uair became 3 frames faster in return for doing 1% less and slightly lower knockback, Fair became faster by 2 frames, had 7 less frames of landing lag, and does 1% more, and Dair gains 1 active frame for its clean hit and cannot spike grounded opponents, but launches them up 80 degrees sort of letting him setup. With the mechanic changes such as no edge-hogging and removal of hit stun canceling to Brawl's degree, Falco can close out stocks easily because of his high KO potential and edgeguard game. None of the patches addressed his major issue: that Falco by design - look at his Specials, Blaster and Reflector, his fast and strong close combat game - is an anti-zoner, but lacks the ability to aggressively anti-zone with a projectile and is reliant on defensively anti-zoning with a Reflector. Falco's forced to play as something that while he's good at is only half of what he is supposed to do.
Things that didn't happen to him, but happened to Fox includes Fox breaking away from having the same air speed as Falco in Melee and Brawl; instead of increasing Falco's air speed, they increased Fox's, who is already fast on the ground. Effectively, assuming Wolf's movement stats don't change as much - fix the fast fall speed for him -, Falco would be the slowest in the air and on the ground out of the Star Fox cast - Wolf's walk speed is slightly faster than Falco's and his run speed is slightly slower than Falco's, so it's kind of tied. That's not exactly good when Falco's already considered one of the slower-moving characters in the game and his saving grace is his walk speed and vertical coverage through his jump. It's also not exactly good when the other high jumpers, Greninja and ZSS, are considered to have the highest overall mobility in the game. Even Rosalina counts along with Sheik while Luigi already runs faster than Falco and at least has a mid-range game to compensate for slower air speed. If this game did go with some logic that Falco is a pheasant and for whatever reason, pheasants can reach high air speed in bursts along with what seems to be good air speed for birds, he could have had fast air speed acceleration like Rosalina and Palutena, but instead he has average air speed acceleration. Since movement stats and such were never touched unless you were a character coming from a previous game like Mewtwo and Roy, I doubt any patches will involve such changes.
So, you end up with a character that kind of plays like a jack of all trades. Falco's edgeguard game is good, but Pikachu's is better and he technically has Pikachu's Fair post-patch 1.0.8; before, it was 2 frames slower and the looping hits hit slower. He has Zelda's Nair post-patch 1.0.8, but it's 3 frames faster in startup, has constant damage, and 4 frames less landing lag. With how his jump works, he can dive deeper than Zelda to edgeguard with Nair, but for all intents and purposes, it's Zelda's Nair. His Uair was a Rosalina Uair - technically, it was his since Brawl -, but without Rosalina's long vertical range, late hitboxes, and low fall speed and good air speed to glide under people. Now? It's a ZSS Uair that does 2% more, but he lacks ZSS's air speed to follow people. Sure, he has the jump height to get right under you and Uair you past the ledge, but ZSS is the 3rd highest jumper tied with Luigi and Greninja's the second highest jumper. That's just some slight jump high differences between Falco and ZSS. Oh, and for the record, Rosalina's the fourth highest jumper and with her Uair vertical range, it more than makes up for her "lower" jump. His footsies are good because of his fast attacks, good melee range, and fast walk speed allowing him to position quickly, but only if he's up-close which he can't really get in that easily because of his overall low horizontal movement speed. His spacing and footsie game is considered good, but someone like Little Mac would outbox him. Hell, even Luigi can outbox him because of Falco's nerfed jab from Brawl to Smash 4. When it comes to killing, he has an easy time due to his arsenal of kill options, but the issue is how he gets the kill. Falco lacks kill setups none of which are true; he's dependent on reads, usually by reading DI after a setup move like Dtilt or strictly reads like landing a Bair, frame trapping with Uair, and basically playing like a counterboxer in a game where people have true combos and true setups out of normals and grabs and where a lot of moves on-shield and even on-hit are unsafe. It's like playing as PM Wolf who also doesn't really have true combos, but without a quick setup and confirm, Reflector, inability to pressure shields, and a functioning projectile.
Justifiably, Falco being able to combo from practically anything even though they're not true is dangerous. Had he moved much faster like Roy or had an abusive projectile like Sheik, Falco could dictate matches heavily.