There were also complaints about the quick defeat of Great Shocker during the movie.

Why doesn't Decade have a world of his own? Well, Decade's color is Magenta/Pink, and scientifically, Magenta/Pink is not on the color spectrum - the color Pink is a combination of red and violet, which are on the opposite sides of the color spectrum, whereas Magenta is created because of an absence in the color spectrum.

But in that world he's most likely a kaijin, so he's probably still around.

given the fact that he transformed into Dark Kiva a total of three times in both here and in Kamen Rider Kiva, we can see that he is as good as dead.

An equally spoilery example is the case of Otoya's unknown fate at the end of the Negative World, although.

Although the In-Universe Hand Wave is that it's one of Tsukasa's special skills that he acquired whenever he goes to a new world, like how he could play the violin, or how he could enter the mirror world.

However, The Reveal of his identity suddenly made it all make sense: as the leader of Dai-Shocker, he would have made contact with the worlds before in order to recruit races like the Gurongi, and in order to study up on the biggest threats to his ambitions - the Kamen Riders.

There were a lot of complaints about Tsukasa's depths of hidden knowledge, including being the first (and so far only) human to understand the Gurongi language and having extensive knowledge of the various worlds despite being an amnesiac.

How do kamen rider movies fit in