"Far too good" please explain. He's similar to those characters now because he solidly loses a few notable MU's. Marth has difficulty against Sheik, DK has trouble against ZSS, MK has issues dealing with Diddy and Mario. Like those characters, he has (a) counter(s) among the top-tier cast that hold back his tournament success. When talking about Pikachu, his Mario MU is often cited as a significant hindrance, and now MK shares that problem.
Falcon, DK, and Marth are commonly considered 20-25 so comparing MK to them isn't wrong.
Djent
Pikachu and Rosalina aren't common characters. The Sheik MU is better after the patch, but in exchange MK struggles more with almost every other top-tier. Instead of having one heavily disadvantageous MU, he now has several moderately and slightly disadvantaged ones. Characters in 10-15 tend to have good rep and gain good results on a relatively consistent basis (eg. Mewtwo): MK has limited rep and his results are currently on a semi-consistent basis. I find it difficult to believe that Leo would drop a 10-15 character for a 20-25 one.
I disagree that he solidly loses said few notable match ups. That is my explanation.
These are the match ups I feel Meta Knight has the most difficulty with. Not necessarily which ones he has disadvantages in, although there is overlap here.
I have labbed Luigi recently and the risk reward is heavily skewed in his favor. If you are DIing optimally against his throw combos the most damage he can net is around 55ish % if I remember correctly, where poor DI bring you close to or over 70ish %. He has a kill confirm at 70-76 with down throw, full jump buffered soft neutral air into Super Jump Punch which, when you know the % range, is not particularly difficult to land. This is important because it is just outside the range of what his combos give him. Fireballs completely shut down approach attempts on the ground, and his aerials are too disjointed and too fast on start up and cool down to challenge in the air. On top of this, Meta Knight's combo game is pretty limited against Luigi compared to what he is usually able to net with a grab or dash attack confirm. He can kill Luigi with a single dash attack confirm at low %, but if Luigi knows the DI it is only 30 % with dash attack 1 and 26-30 with dash attack 3. Off stage Meta Knight has a decent chance to take Luigi out but getting him there can be difficult and if you are not positioned properly it is difficult because of how fast double jump Super Jump Punch is from the bottom blast zone. Fireballs do 5% from a distance which is non-trivial given how light Meta Knight is, and if he makes a single mistake he'll die at 52-36 depending on rage from Super Jump Punch. Where Luigi struggles in this match up is when you have a lead but getting that lead in the first place can be difficult because his neutral shuts yours down.
Not impossible to win, 4:6 at worst, but it is very arduous and making one or two mistakes often loses you a set.
Game & Watch is 5:5 in my opinion but the match up is difficult due to how the characters play so similarly in the risk reward department. Neither character can approach very safely. Both have difficult to punish dash attacks, both have low risk high reward smashes that will kill each other if one makes the foolish attempt to punish the other for using them, both are light, both are hard to edge guard. If Game & Watch lands a grab he nets a lot of % due to Meta Knight's fall speed and weight, and Meta Knight cannot afford to get grabbed between 87-102 or he's going to die to down throw, up air. Consequently Game & Watch will die at 78 if he gets hit by dash attack or forward throw. Meta Knight needs to be very careful when he chooses to dash attack because if Game & Watch happens to up smash when Meta Knight commits he is likely to die for it. Down throw to Judgement is always a concern as well. One of the edges Meta Knight has is that he can kill Game & Watch with a ladder confirm, but since neither character is able to approach easily fishing for this is not guaranteed.
Regarding Marth and Lucina I have done a post
here regarding my thoughts but I think it is 5:5 to potentially 6:4 in Marth and Lucina's favor.
Corrin is difficult because it is very hard for Meta Knight to land against a Corrin who keeps stage control well due to forward and up air's disjoints, and trying to commit to an approach option against Corrin is always a risk due to Dragon Lunge. While dash attack can clank or beat Dragon Lunge the Corrin can just retreat and bait with the move, in which case the obvious decision would be to go deeper which runs the risk of an immediate Dragon Lunge. It becomes a 50/50 situation that nets Corrin 19% for guessing right, and if she guesses wrong she can retreat. She gives up stage control so this decision is not free, but you are always respecting a large zone of her play. Also, Dragon Lunge has a tendency to kill Meta Knight at 60% ~ on a whim which can drastically turn the tides. Corrin is also very frustrating to edge guard because the F10-17 intangibility and sheer hit box size on Dragon Ascend is so obnoxious that she usually gets to the ledge for free. On top of this, once she is on the ledge she has a lot of options available to her and keeping her from getting back to the stage is difficult without a lot of risk involved. Corrin's issue in this match up is she cannot land, dislikes playing from behind and she gets combo'd pretty hard, though down air is annoying since it can be difficult to punish depending on spacing if you choose the wrong option when she lands due to it having a landing hit box.
Like with Marth and Lucina, I could see Corrin be 6:4 in Corrin's favor but 5:5 is reasonable too.
With Sonic there is a lot of technology that can be used against him. Neutral air beats Spin approaches, and depending on which option Sonic opts for when hitting your shield Meta Knight can net some punishes. However, regaining a lead Sonic is likely to obtain is not easy and this is usually what dictates the match up. I could see 6:4 in Sonic's favor.
Bayonetta's neutral is underrated and it is difficult to approach Bayonetta with the tools Meta Knight has without risking getting hit with a confirm or Witch Time. While she cannot do as much as she could in the previous patch she still does a lot of damage per confirm even with SDI. She is very difficult to juggle, Bat Within gets her out of conventional combos and she is like Corrin in that edge guarding her is very difficult since Afterburn Kick and Witch Twist have too much priority. I feel this match up is likely 5:5 but can involve a lot of patience and risk.
With Little Mac, it is likely 6:4 in Meta Knight's favor but it is quite easy to lose this match up on one or two mistakes. If Little Mac is off stage it is very easy to get the upper hand but getting a patient Little Mac there is difficult. You need to know when forward tilt and forward smash will create too much push back to punish, which forward smash will cross up your shield, and when to and when not to shield to avoid a shield break. The entire match up is based on playing around moves with trample and super amor, which makes landing conventional confirms difficult and risky. Despite being a character with wings, Meta Knight is usually a very ground paced fighter, and no one ultimately "wins" against Little Mac on the ground. Down air is very valuable here, but landing at the wrong time is a risk. And while the match up is already swingy, K.O. Punch confirmed off of a down tilt kills Meta Knight at 0.
Sort of the opposite to Little Mac, Ryu is likely 5:5 but could be 6:4 in his favor due to how strong his punish game is and how early he kills, however he is rather poor against well spaced defensive ground play and Meta Knight has a lot of tools in this match up to defensively react to his commitments while also having options for offensive pressure that are decently safe. However like Little Mac this match up has to be played carefully since one or two mistakes loses you the game, but I would argue it is much less frustrating.
Megaman, Pellets.
I do not know where this idea came from that Meta Knight loses to Mario, but it is likely even at best for Mario, if not 6:4 in Meta Knight's favor. Mario is not particularly fast on his feet, he loses to disjoints, and a lot of his kills come from up smash which should not be landing on a character with multiple jumps and Dimensional Cape. I feel Fox is even. Fox gets combo'd hard, is one of the easiest characters to kill off stage, loses to disjoints and gets all of his confirms off of moves that lose to shield. While Meta Knight cannot match his frame data the disjoints makes up for this discrepancy and Meta Knight has the ground speed and movement to keep up. I have reconsidered Diddy to be likely even also given that Diddy is too reliant on his Banana against a character that has really good item play. Banana does not shut down Meta Knight's approaches as hard as one would believe and Diddy is in an awkward position when he is without one and needs the time and space to pull it out again. Sheik I have gone over enough already.
The reason I posted this was because there is a difference between having an advantage and having it easy. This is why you are seeing Mario do so well in top level play despite him ultimately losing several match ups he has to face. Meta Knight is not an easy character to win with, but that is not necessarily because he loses the match ups he has to play in.