Since Pikachu was brought up and it got a placement I actually agree with in the official tier list, I think I'd like to go over what I believe Pika's weaknesses to be:
1) Low damage per hit. Now of course, we all know Pika has a strong combo game that helps mitigate this, but still. In scramble and trade situations, the mouse does not have numbers on its side. Pikachu is the only character I play where I think, "Wow I did so little damage". I think this is something people didn't take into consideration with their early evaluations of Pikachu. Yes, it has a strong combo game and very good neutral tools, but more often than not, it will find itself in situations where the opponent is at 60+ percent. Its strong low% combo game is done, and it hasn't gotten one of its rare, read-dependent strings that kill early. Racking up more damage will now be a slower process than most other characters because its moves do low damage individually. And it's going to have to go through that slow process, because...
2) It lacks anything with explosive kill power. I'm aware it has some zero-to-death combos, but how often are those pulled off by even Pikachu's best players? Probably twice a set at most, and they are very frame-tight and probably don't work on a good chunk of the cast. If you're not getting those, and not getting edgeguards, Pikachu is going to have some trouble killing. As far as edgeguarding goes, we overvalued it early on. It turns out, the vast majority of recoveries in Ultimate are strong enough as to make edgeguarding a very risky option most of the time. Not only is your opponent likely to make it back, they may very well reversal you, leading to a stock loss. So Pikachu definitely has to pick its edgeguards carefully, especially since, while it has a great recovery, it's only great if both zips of Quick Attack are executed... and we've all seen good Pikachu players, even ESAM, just barely not nudge their joystick enough and not get the second zip. So it's definitely something Pikachu players have to be mindful of. But back to explosive kill power, look at it this way: Incineroar has a strong, armored command grab that kills very early, especially if powered up by Revenge. Characters like Byleth and Min Min have long-ranged smash attacks that can kill extremely early. Pikachu simply isn't killing that early onstage, giving it less ability to cheese stocks than a lot of other characters. We undervalued the ability to cheese stocks early on; look no further than MkLeo's Byleth f-smashes and Skyjay's Revenge-boosted Alolan Whips for exaamples of how strong such tools can be. When Pikachu's opponent will live a lot longer more often than not, it presents more opportunity for them to make comebacks. And just so we're clear, I know Pika's dash attack and forward air kill around 140, and up throw around 160, so I wouldn't say it has a lot of trouble killing. But some. Those are pretty late %s for Pika's opponent to live to, when a lot of other characters consistently kill a lot earlier than that.
3) Lack of range. We all know how strong sword characters continue to be. It can be difficult at times to get in on them as Pika, as well as some characters who don't use swords such as Wolf and Min Min. While not necessarily bad matchups for Pikachu, they definitely make things more difficult. While T-Jolt is a strong projectile, it is both a little slow to come out, and has some endlag. Imo this gives Pikachu a healthy amount of counterplay to how it can approach neutral, especially by characters with long range.
While these are pretty small weaknesses, I think they all add up enough to be the reasons why Pikachu fails to be the dominant force people made it out to be. The characters above it on the tier list tend to only share the flaw of lacking explosive kill power (base Joker, Sonic, Diddy), or share none of its flaws. I am by no means calling Pikachu a bad character. I just don't see the "busted, absolute best character" so many seemed to see, and instead, see a pretty solid top tier. I don't abide by the whole "results don't matter" thing. It's been four years. If Pikachu was this amazing, absolutely-best-character, we would see Pikachu players dominate. But we don't. I don't care that the character is said to be hard. It's been so long that the difficulty of the character should have been largely mastered by its best players to allow it to dominate. And it just hasn't. Its best players place very well most of the time, and ESAM has placed first on occasion... but not nearly often enough for me to view Pikachu as the best character, or even that close to, anymore. Pikachu should pretty consistently be placing first and second if it's so "busted" at this point, and it just isn't.
