I like very much what you said, I agree with you, and I also sometimes play it that way in order to take less damage, especially when I have an unsuitable ability and I don't want to change it (because maybe there is a section where it is very useful later).
Anyway, those people I was refering to, are haters, they say the game sucks because it's slow and has bad controls, and it's so slow that's uninspiring and boring. They are not refering to the difficulty level and to the risk, they simply say that's boring and uninteresting.
Probably those people don't know that you can dash if you double tap the direction; Dreamland 3 is pretty slow if you don't dash.
It's not much frequent to read people hating this game, they are not that noisy, but there is a part of the fanbase who hates or simply dislikes Dreamland 3, and they come out occasionally... I can see why some people may not like the game, but I don't like when people trash it (and give it a bad reputation) using fake arguments. It happend more than a couple of times that I had to fight with someone about this matter... I already made another video (I haven't uploaded it yet) where I compare Dreamland 3 and Superstar's running speed and they appear to be exactly the same, with the difference that Dreamland 3 uses smaller units and if you scale the speed the result would be that Dreamland 3 is faster, about 1.6 times as fast as Superstar (I'm talking of actual speed and not about how it feel), so that if in the future I will find another person hating the game using that argument, I will link that video to show the truth.
About what you said, it's definitely true, though I don't see that as slow, but as challenging.
If you go slow but you still have little time to react to an hazard, even if you are moving slowly, you must react in a certain time and if you don't you will be punished, so you can't distract, you can't get bored (an example of this is the underwater gameplay, underwater DL3 is very slow (unless you use Kine), but the bubbles require a great precision in order to hit, so even if it's slow it still keeps the player involved enough to be a challenge).
It's like, for example, Dark Souls (yes, I'm comparing Kirby to Dark Souls), your character moves slowly, the attacks have a lot of lag, you must be precise and every error is punished; even if the gameplay is slow enough, it can't be boring, since you must constantly watch out the environment to prevent surprise attacks, traps and so on; you are constantly in a situation of danger.
This can be applied to other games, like FPSs, when you procede slowly, hiding yourself behind walls and looking around before entering in a new room, because if you enter careless, the opponents will kill you... or even worse, in stealth games, when you must hide yourself and stay in place until you find an open.
And yes, Dreamland 3 is probably the hardest Kirby game to master, even though it has simple movesets, it's a lot more like Smash Bros than any other Kirby game, because each attack has a delay and an endlag, and a precise hitbox; it reqires you to be precise, manage the space and the time frames, you can't play careless.
To be honest, this is the reason why it's my favorite game, and while I like the modern Kirby games, I think I feel less motivated to play them since the movesets of the abilities are so overpowered and there are all those invincibility frames; they miss the challenging aspect (I spent countless hours on Triple Deluxe and I love it, don't get me wrong).
Even if the true arenas are hard, I still feel like exploiting the invincibility frames of the dash attacks is not as fun as dealing precise attacks with precise timing and spacing.