For one, Meta Knight was not recently viable due to patches. Ito was making waves in Norcal and Socal with the character prior to that against high level players. They made him better, but he was easily top 15 prior to.
Secondly, purely based on match up spread, I would say Meta Knight has top 10 characteristics. He loses to Zero Suit and Sheik by general Meta Knight consensus. All of his other match ups are either 5:5 or in his favor, and this is not some Greninja/Pac-Man/Ganondorf/Radical Larry board nonsense.
Lets look at the characters that I firmly believe are better than him:
These are the best characters in the game from where I am standing. They have the highest rewards, strongest kits, most options, explored and unexplored potential, and all of this is backed up by results. As long as you're not naive enough to believe that a player is carrying a character, like Ranai being the best in Japan and ESAM being top four in the US, then this makes factual sense. Ryu is more questionable, but what do you expect from a recent DLC?
Let's look at the characters I see people rate highly but are more debatable on their placing:
Luigi recently just got nerfed. I think that covers that topic.
Mario is the hardest to call. He has a good match up with Sheik, a good match up spread, excellent overall frame data, and like the top 7, plenty of options. However, his recovery is rather poor and he lacks reliable kill confirms. He also lacks the over the top options the other 7 do. He doesn't have Luma, he doesn't have Sheiks Needles, he isn't killing you at 60 with TSRK, 30 with Boost Kick, et cetera. He does well because he is easy to play, he has the options of a top tier, and player style is easily translated with his kit.
Sonic is overrated. Like Olimar, he struggles when playing from behind, and people have not properly explored how to punish his approach options when he picks a particular approach option, or how to use character specific options to prevent him from approaching risk free with Spin Dash. He also has problems with kill confirms, and has a very binary style of play.
Ness loses too many match ups against the top tiers too easily. His recovery is very exploitable even in match ups where he should win, making him a volatile pick. He loses to Sheik, Rosalina wrecks him, and I am willing to bet characters like Mario and Villager do too. Once people start learning to not choose Smashville against him game 1 and how to DI his back throw while also keeping specific stage advantage, he will be doing even worse.
Fox is also overrated, though much less than Sonic. Fox has excellent tools due to his mobility, but he loses to any sort of priority, and the top 7 have those in spades with the exception of Pikachu. He also has a very unsafe recovery that still does not get exploited properly at high level play, and all of his confirms that he needs to get are unsafe on block.
I feel R.O.B. is vastly underrated and is likely better than Meta Knight, but it is difficult to call. Excellent CQC, an item game, a Gyro that instantly respawns when its gone, good frame data, excellent combos, kill confirms, good recovery, very safe. I am unsure of his overall match ups.
Meta Knight has the best overall recovery in the game, alongside Zero Suit, Sheik, and Villager. He has one of the strongest edge guard and ledge guard games in Smash Wii U. He has the ability to kill characters as early as 10%, with most commonly dying between 25-40, with the only other character capable of this being Zero Suit. With optimal play, characters die on average at 80 from simple conversions. He has some of the highest damaging, straight forward, non-item related combos of any top or high tier. While his neutral is not strong per say, he had one of the safest neutrals. He does well on literally every legal stage and can win match ups purely off of map flexibility. He has a strong advantage and disadvantage state, and is able to kill you easily in both. He has some of the best mobility. He is among the best characters in the game with rage. And he arguably has only two 4:6 match ups.
The reason you're not seeing Meta Knights place higher yet is because everyone is **** with him, and they don't understand him because they have not properly labbed with him and understand the necessary %'s for his conversions, basic ones included. He seems somple, but players like Mr. R and Tyrant, who have prestigous reputations as competitors, are doing suboptimal combos and unsafe carnival tricks when then should be destroying people.