Google and Apple have a duopoly on mobile platforms, which are the natural place for any communication app. If those two act in concert you are facing a monopoly. There are only two ways out. Competition or regulation.
For AWS, I agree there are many alternatives, and in fact what shocked me wasn’t so much that they terminated their contract with Parler, but the fact that they seem to have done so with zero notice period. Which I find extremely cavalier.