Kirby and the Amazing Mirror is what Majora's Mask is to Ocarina of Time. Sure, it might feel a little on the shortish side and some changes might not make a lot of sense, but it's pretty much a superior sequel that offers more depth and challenges than the original had to offer.
On top of that, who can say "no" to using the powerful endgame ability outside of the boss fight? It's something that I don't think hasn't been done before in a Kirby game prior to that.
On top of that, who can say "no" to using the powerful endgame ability outside of the boss fight? It's something that I don't think hasn't been done before in a Kirby game prior to that.