I agree in that Meta Knight is good, but I still wouldn't put him above 12th best. He's perfectly viable, but saying that he's in the 6-10 range is ludicrous. What makes him better than Fox? What makes him better than Luigi? What makes him better than Diddy Kong? Better than Yoshi? Than Ness? Than Sonic? Than Villager? Than Ryu?
I'm not buying it.
It's very easy to be better than Yoshi for example, likely the same with Villager and possibly also Ness, and they're all better characters than Luigi now. Yoshi doesn't have safe approaches, gets nothing out of grabs, and doesn't have non-committal kill options. His main strength is pressuring you with his aerial speed and fair offstage and trapping you in the air with his nair and uair where shield isn't available to you. He's a good character, but he can seem overwhelming when he shouldn't if you don't abuse his lack of safety and linear options in neutral, especially when it comes to approaching and killing. He dies to disjoints and good rising SH aerials as well, and he can't really approach on the ground because his dash attack and dash grab are both slow and laggy. Eggs aren't safe either except sort of if Yoshi puts himself in the air first, but then he's counter-productively vulnerable because of putting himself in the air. Not going to go into the other characters, but I'll mention that Ness is still mostly being overrated because it's easier for Ness to abuse his strengths than it is for the opponent to abuse his (glaring) weaknesses that will only become more and more apparent with time. He also lacks mobility so his depth can't get developed too far relative to faster characters.
MK is a strong character even outside of his uair to up b combos which alone would make any character a serious threat, and his only considerable flaws are bad SH aerials in neutral and low damage per hit. Falling bair spike into ftilt jab lock into death / a lot of damage however is about as real as Ike's footstool setups, although probably even easier to get started. MK has a great recovery and edgeguard capability, dash attack into up b kills at 90-100% and is guaranteed, up b OoS kills at 100%, fsmash is safe to throw out whenever, down b is a very viable kill move, bair kills, ftilt kills, and nair kills. I don't even know if tornado is commonly used on high level but it traps airdodges and also kills. Despite MK's low damage per hit, I think he ultimately racks up damage well enough through combos, juggles, setups and edgeguards, doesn't have trouble getting kills, and has a super threatening low % kill setup. When it comes to neutral though MK is basically an objectively worse version of Falcon. He has the same gameplan in neutral with slightly worse overall options for approaching and zoning/spacing alike. MK has to commit a lot in neutral and is lightweight, and I think that's the only thing holding him back from being something like top 5. In my mind he's 9-10 with Pikachu, behind Sheik, ZSS, Sonic, Rosalina, Ryu, Diddy, Fox and Mario.