There is an important aspect that people don't seem to understand regarding the cameos, mainly those who say that the cameos are unnecessary and pointless.
The reason for the inclusion of all this high-profile celebs is of course to draw attention to the video. But most importantly, it has to do with the message of the song. All these stars are Madonna. We are all Madonna. Even the 4 little girls in the beginning are Madonna. We are fearless, strong and we can do anything. This is how I see it.
In addition to the fun, colourful part of the song, this is meant to be empowering.