When I wasn't too much into Kirby (just after finishing my first Kirby game, that was Kirby's Adventure), I thought that "Dreamland" was actually the world of the dreams, kinda like NiGHTS if you know. I admit that I liked very much that concept and I was a bit disappointed when I discovered that Dreamland was just the name of the country. I thought that each cameo (Mario & co. in Superstar, Samus in KDL3, etc) was due to the fact that those characters were dreaming, and they met Kirby in the world of dreams. Maybe it's a stupid theory but I thought it was interesting back then.
Also, there are rumors that Shiver Star (K64) is the Earth, since it's pretty much identical, moon included, and there are some danger signs that are similar to real ones. A frozen up Earth, probably in a distant future... this makes me thinking of Pikmin. Looks like the planet of Pikmin is the Earth in a post-apocalyptic future where humans are all gone and only some insects survived.
That's obviously all speculation.
I agree with you, and I'm the first one saying that there shouldn't be any human character in Kirby, but I'm strongly against scrapping characters also. Ado/adeleine were part of some classic Kirby games, canceling the existence of those game would be simply a bad choice. It happens that I love the concept behind those characters and especially the art style related to them, and that's why I'd like to have them back (I think Adeleine alone is more than enough), but that's not the only reason why I want those characters back. As a Sonic fan also, I feel betrayed each time Sega introduces a new character, and then after a couple of games they cancel its existence like if it never existed. It happend so many times (Ray, Mighty, Fang, Bean, Bark, GMerl, and recently other characters like Big the Cat and Cream the Rabbit are slowly going to be forgotten). The fact is that Adeleine would actually adds something to the franchise. You can't simply replace her with Paint Roller, they have completely different personality, completely different art-style and a slighty different concept. Also, just like Bandana Dee, Adeleine has been helping Kirby during one of his adventures, being one of his main friends in a game... I can't forget about that, I don't want to forget. She is one of my favorite characters, that's one of the reason why I like the Kirby series so much.
I think it's unfair removing a character because it's "human", when Sakurai put Mario, Luigi and Peach into his most important Kirby game and nobody had any problem with that. There are other creatures looking like chibi humans in Kirby's universe, like Poppy bros. and Knuckle Joe, and the Bonkers, despite being more like monkeys than humans, have human-like proportions and traits, so much that they almost feel unfitting. I don't know why Adeleine should be a problem.