Kirby Triple Deluxe was a pretty average and decent Kirby game for me. There are definitely things the game does well and parts that I enjoyed. For example, the colors were vibrant, the animations excellent, and the levels well-themed. The use of space and multiple planes was actually a very interesting and well-executed mechanic and I can imagine it looking amazing in 3D (I played this on the New 2DS XL). I liked some of the new copy abilities (though Circus was by far the worst power) and appreciated the variety of moves you could perform with each ability. For example, some moves had at least a dozen different button combos that would perform various attacks. I liked the sections that took your ability away temporarily, forcing you to go through as normal Kirby for a while. I also appreciated the item space on the touch screen--it was nice to store an extra health boost for quirky boss fights, though I rarely needed it until the end, when multi-stage fights got extremely tough. Strangely enough, many bosses were actually easier when using the standard "inhale stars and spit them out" strategy rather than trying to get close enough with a copy ability. I am still split on the Hyper Nova ability, though. It's clever and had some interesting applications, but it kind of just felt like pressing B in front of different kinds of obstacles.
I think my favorite part of the game was the "extra mode," Dedede Tour. I thought it was much more fun than the normal mode, mostly because there weren't any distractions and Dedede's moveset is excellent. As far as extra mini-games go, the rhythm-based one was tricky but oddly satisfying once I got the hang of it. I confess to not having tried the Kirby Fighters, but apparently it was popular enough to get a spin-off.
Based on these aspects alone I would recommend the game to Kirby fans, especially since it's worth the $20 price tag you'll find on used copies. However, I think there are much better Kirby games and I do have some gripes about Kirby Triple Deluxe.
My main gripe is with the collectibles. In past Kirby games, collectibles are either a) challenging or b) worthwhile. Sure, the sun stones unlock extra stages, which is great, but it was completely unnecessary to lock the boss fights behind gathering them since they were so blatantly easy. A rare couple were a bit tricky and/or frustrating, but half the time the game just gave them to you for free. For a perfectionist like me, I spent half the game overthinking where they might be hiding based on my experience with past Kirby games, which took away from my enjoyment of the game. Again, the extra mode was so much more fun because I wasn't worried about the collectibles and could just enjoy speeding through the game. If this sounds like a personal problem, I admit that it is. However, the other collectibles, keychains, are completely pointless. Not only are they randomly generated, which makes getting them all a matter of luck, they don't do anything. They're basically just legacy icons from older games. That's it. If they were more like Smash Bros. trophies with information or trivia, or if there was some sort of mildly interesting activity you could do with them, that might make me feel more inclined to get them all. But they just kind of sit there on your save file. Personally, I love Kirby collectibles that change your skin color, or give you new abilities, backgrounds, maps, anything useful.
You can absolutely enjoy the game without worrying about collectibles or my petty grievances, which is why I still recommend it, as it offers some fun gameplay moments. It just felt a bit shallow and artificially padded.