“something with zero mass like light”
Light only has zero rest mass, and since it is never actually “at rest” that seems like a pretty flimsy objection.
“We see effects that may be caused in this manner, or may be caused by other phenomena.”
One could say that about every single scientific proposition ever made. The best science can do is rule out some explanations, and then try to judge which among those that remain can best explain our observations. Still, there will always be alternative explanations that might be true, which science cannot rule out.
I believe we’re at the equivalent of an end-of-geocentrism moment.
As accurate as Ptolemy’s epicycles may have been, they were not a correct physical description of the real world universe.
What is going on now, primarily, are the specification of the modern equivalent of epicycles in extraordinary - yet still incorrect - detail.
We have enormous evidence that the Big Bang cannot be true. It requires many absurdities to set up; it requires absurdities to maintain. It conflicts with what we can prove about quantum mechanics, and pushes its uncertainty into structureless phenomena that can’t be observed and thus cannot be falsified.
Today we have reached a point where 97% of the universe is said to be made of non-falsifiable stuff. This cries out for new explanations - explanations that will not be had by further pursuit of epicycles.