We do?
Looking around on the Megaman boards for match-up threads, I rarely, if ever, see any discussion about Megaman vs Metaknight. I think the most problematic match-ups for Megaman that appear with some frequency are usually faster characters that can get past pellets, like Fox or Shiek, or those with projectiles that are more spammable like Rob.
Not really much Metaknight discussion over at the Megaman match-up threads.
Granted, I don't have much personal experience in the match-up.
On the competitive thread i clock posts being pretty pessimistic about MK, i don't think its bad at all though.
It doesn't kill purple pikmin as purple pikmib does not stick 2 player
It takes 2 dtilts after 1 up throw to kill purples. They all bundle together when MK sends Oli up so they always get hit by MK who's turned into a hitbox on the way down.
Just because Meta Knight has a favorable matchup against some of the characters above him doesn't mean he should automatically be higher than them on a tier list, otherwise Samus would be joint top tier with Fox on the Melee tier list. A tier list shows where a character sits when taking all matchups into account, and Meta Knight has a lot of difficult ones because of his lack of reach and projectiles combined with his minor KO power. Toon Link for example absolutely floors him with his projectile wall, none which Meta Knight can absorb with his Mach Tornado.
For the most part Meta Knight has decent matchups against a lot of the cast, but there are very few that he counters and a good handful that hard-counter him (Lucario being the most notable), therefore he logically ends up as being a bit below average imo.
If MK had Kirby level mobility then he would struggle against ALL projectile zone based characters, which certainly isn't the case Kirby can get walled for days by Tink once Kirby gets in Tink can haul ass and run with his overwhelming dash speed. He cannot wall a MK who's running into shield and staying at mid range allowing him to punish his moves on reaction, when Tink has no bomb in hand he's pretty helpless.
When you're a fast character there's no need to be afraid of projectiles when you can dash into shield to close alot of ground. He has similar sword range to MK, but lacks good mid range options against MK without a bomb in hand. Also 6 jumps and you still get walled out hello?
Lucario is only hard because if you miss your kill setups you're screwed, atm no MK users other than Itol is abusing Dtilt kill set ups which can kill more reliably than others. At high percents down throw should never be used its so easy to DI, if you wanna kill use forward throw into SL.
Taking Lucario to low ceiling stages is a dream, sadly helbird gets stage striked first cause its rule no.1 against a MK, so TnC is the next best thing i guess. Will say its in his favor since MK users need to refine his vast kill confirms, he's definitely not a hard counter.
MK has 2 somewhat booty MU's one of them becoming less scary(by alot) if you don't take him to FD.