Amazon is well established. Amazon has thousands of employees. Amazon does, ultimately, provide a good service. But Amazon is also dominant, demonstrates a callous disregard for worker rights in its other business arms, and has used its solid AWS profits as a way to prop up its undercutting and dismantling of other sectors.
Other businesses will not enter the space in as developed a state as AWS. That shouldn't be used as a negative against them even trying. Otherwise, AWS is only going to become more entrenched and the options for building at scale will become more limited.