The problem here isn't Amazon, it's the other Bezos company Blue Origin. They're older than SpaceX, but have yet to launch even a single gram of payload into orbit. Two of the three rockets Amazon contracted for Kuiper rely on the Blue Origin BE-4 engine, which has been suffering delays and production issues.

Meanwhile SpaceX has the highest launch cadence in the world, and is the only viable near term alternative launch provider. Rocket Lab's Neutron may be another option in a few years, too.