Actually I'd say he has disadvantages against Falco, MK, and Pikachu, and probably many more that are arguable like Pit, Toon Link etc.. Lets Face it Kirby's overall matchups against potentialTop/High Tiers is not that good at all. I'd say at best he's around the top of Middle in a 6 Tiers system with Top, Very High, High, Mid, Low, and Bottom.
That's exactly why he at least places in the middle of tournament standings. Pit, Pika, and MK all only have slight advantages. Pit has arrows, but has difficulty landing bairs against Kirby and must rely on the fsmash to KO Kirby. Kirby can also gimp Pit easily and lives longer. However Pit's arrows make up for the fact that he dies earlier as Kirby may take 5~10% approaching. Aerial Hammer saves him from horizontal KOs and Pit sucks at KOing vertically.
Pika Does have good priority on his fair, dair and dsmash, but his fsmash can be difficult to land on someone that prefers the air and is outprioritized otherwise. He gets a slight advantage from Thunder. Thunder Jolt is a moot point because you can cancel them out by holding down "A" or stealing his power and spamming back. Pika gets the slight advantage.
MK has great speed, but Kirby kills notably quicker (under 100% on a regular basis) and dies much slower (usually 120% or more). Neither can gimp each other effectively (Shuttle Loop against dairs and Stone against shuttle loops) and neither have projectiles. Kirby's bair has amazing priority and is a low time sex kick as well and is still very effective in approaching. Overall MK gets the advantage due to his high ground speed and better priority. However, this match-up is very manageable for Kirby.
Any Kirby that loses out against Falco need a new main, srsly. Lasers are ducked, he can't be chaingrabbed at all, starshot outprioritizes phantasm and gimps Falco, almost completely outprioritzes and outranges Falco (notable exceptions include Reflector, ftilt, and dair from above), and he dies earlier as well. This match isn't even at all, its 70-30 for Kirby at least.
Toon Link has projectiles and that's it. We all know how hard it is to chain attacks outside of his bair and his recovery is very predictable and easily gimped. He can even be gimped out of his tether since he reels in so slowly. His projectiles are canceled out in the same manner as Pika's with the exception of bombs which happens to leave an opening if he gets to close. Kirby also lives longer unless killed with an usmash and can kill under 100% without gimping.
The only really notable soft counters are IC and Zelda, but then even they underperfom at tournaments.
Most of his matches are neutral or negligible advatanges, with a few counters and advantages scattered about. At least he's not overhyped like TL and Zelda.