The RtDL style games didn't not have puzzles in their levels, but I think they absolutely emphasized them more in this game, using combinations of copy puzzles and Mouthful Mode puzzles. The game also pushes the focus on exploration with its mission system. You want those Waddle Dees? It's not just about finding them, you gotta pay attention, gotta do weird things and find secret areas to save all of em. Older Kirby games were more straightforward in that regard. I tended to find the collectibles the first time through, only a couple of levels here and there giving me any trouble. Here? In almost every level, I am missing at least one objective the first time I play.
The theming of each level also goes a long way in helping them feel memorable too. In older Kirby games I remember worlds. Not individual levels, unless there is a particularly notable one or the theming is specifically stand out. And even then there's some repeats. Using Planet Robobot for example, I remember the train in World 1 and a train in I think World 5? I remember the two ice cream factories, and the two casinos. But in general I remember that there was a grass world, two city worlds, a oil rig desert, a mechanical-like water world, that kind of thing. In Forgotten Land, so many of the levels go to great lengths to present a sense of place within their worlds. I already gushed about Wondaria Remains in particular (having completed four worlds, it is still my standout favorite), but you see it from the beginning. I don't remember every single level perfectly in worlds one and two, which I played last week, but I remember the city level where you scale the building, I remember the mall...all that kind of stuff. That being said, outside of themes I really love, I wonder how much exacts I'll remember when I'm not playing - though I wouldn't call that a failing of the game.
By contrast, I do feel like the game has deemphasized the combat elements from the prior games. It's still there, but I find that I'm focusing more on the platforming and navigation than usual. Abilities have simpler movesets, there's less abilities than usual, and Mouthful Mode puzzles are typically that - puzzles, with enemy combat being more simplistic in those scenarios. There's been some good bosses, and the different boss level objectives and bullet time dodge mechanics add good incentives to learning the patterns, but there's also less mini bosses. Combat in general feels less precise in the 3D space, too. The camera thing does a good job of making it still feel good, but in 2D it is very exact, and that's hard to replicate in this style. The bonus levels do a good job of keeping up the action, but it is a different kind of action, I find, and they (reasonably) don't have the same level of theming as the main levels.
Of course, if you're here for the explorations and the puzzles and the uniquely themed levels and only kind of care about Kirby's beat em up elements, this isn't a big deal. But it has been noticable to me. It makes me want to see Attempt 2 at a 3D Kirby game, one with more abilities and the combat tuned up just a little more. Maybe there's a big shift that happens in the last few worlds, but outside of having a bonkers final boss (as usual) I'll probably still feel this way - great game, but I know very exactly in what ways I'd like to see tweaks for a follow up.