I was actually going to make a thread like this, but you beat me to it :/ Ill give you as much knowledge as i know, and trust me... after playing around with Kirby a lot, i know A LOT about his whole moveset. Some "useless" moves, are actually useful if you use them right, which a lot of people dont get. So Ill do my best.
Inhale: inhale has tons more uses than kirbycide or copy. Think of it similar to how Wario players use chomp, or Bowser players use koopa claw. It's really good to mix up this move when the opponent expects an attack so it goes through shield and does 10% it also beats most moves in the game, ex. All of Sonics specials, squirtles side b, luigis down b, Wario's side b, Bowser and DK's Up-B, and the list goes on.
Final Cutter: A mixup for the cutter dash, and will almost always hit because they'll expect a Cutter Dash. Sends a projectile to help for edgeguarding. Best used on the ledge, ledge cancelled FC forces them to tech chase which could then lead into a punish if you react/read them correctly. Can also meteor if you grab the ledge backwards when using it, which sets up for amazing edge guard opportunities if they meteor cancel it.
Cutter Dash: Other than the approach potential this move has, it can help with combos. Ive comboed this after an up-tilt and then comboed this into a hammer on certain characters at like 60% and killed. It can cancel laglessly into slopes where you can grab or w/e. Can also cancel lag on the edge of a stage, i recommend Kirbies should all know how to do this consecutively.
Rock: Amazing combo potential. No one uses it, which is sad. It works basically like Falcon's dair that can be used multiple times. Can combo into hammer or aerial hammer pretty reliably at around 50-60% (falling speed dependent) and can kill if your on the edge. Best used if you edguard them and they have to recover back onto the stage. I also think there is a use to this to use kinda like a dair, bait your opponent by jumping over them and punishing with this move. It looks noob, but its way more effective since rock is a lot faster.
Utilt: Really good move. Has more range than it looks like it has. Beats out a lot of moves, and clanks with almost everything else. Can juggle, set up for kills, or w/e. Basically sheik's ftilt in utilt form.
Usmash: I love this move. Isnt no Fox usmash, but has power. Kills reliably below 100% on characters who arent heavy or fast fallers. Really good anti air if you time it right. Use a lot out of sheild.
Fsmash: Beats a ton of moves (may list these later) and is good for killing. Very similar to Falco's fsmash, but better.
Dsmash: Ill guess that this is his fastest smash. Its really good for edgeguarding since it sends the opponent at a horizontal angle if they dont sweetspot.
Uair: The combo move. SH AC uair can juggle like every character and sets up for kills relatively easily. The single most reason I think Kirby has better combo potential than Falcon just because of the angle it does. It also can kill pretty easily, and can semi-spike if you hit them with the back end which is best used as an edgeguard.
Bair: Although Kirby has better aerials now, bair is still very good. It can be wavelanded out of, auto-cancels a mere frames after the hitbox is inactive, can help in spacing, zoning, and can kill.
Fair: Kirby's main approach move in Melee, and can still be used effectively as an approach in PM too. It can AC after a SH which really leaves barely any room for you opponent to hit you. Combo's pretty nicely. Can L-cancel it into grabs. Its basically a Falcon Nair with less range, use it alot like he does, but mix it up more since you have more options.
Dair: I think this move might have invinciblity on the tips toes or something, because I've straight out beaten some crazy **** with this move lmao (like the beginning of Ness' PKT2). Can combo into a foostool if you position yourself right, transforming this move into a true spike. Pretty good approach move. Can trick your opponent that you'll be in a position to attack them if you full hop with it. (since you can either jump, or it auto cancels). A lot like Fox's or Mario's dair, but better.
Fthrow: Very underrated move. Does much more than being "useless" or to "set up for and edgeguard". It sets up for DJ Fair, Hammer at around 70% and kills, CD if they DI down which could then be comboed into more aerials, and probably more. It IS better than up-throw,more so at mid %s. People need to realize the combo potential in this. People will want this move nerfed after people start using it lmao.