You can't prove those measurements are not refraction of light on a surface. The wavelength of light changes when it passes through anything.

In other words, even background radiation and redshift are not provable as NOT being caused by, for instance, the surface of a bubble refracting light in a closed system. That would also explain why there is light going in every direction, aka "everything is moving away from each other" heat death religion.

That's not science, but guesswork built on basic assumptions that are not provable, it's all measurements in a void. If the universe was proven to be a closed system, all that science and your whole cosmology goes in the bin.