When we look to the distant farthest reaches of the universe we see light that was emitted at the big bang 14 billion years ago. But the universe was tiny back then so that light, which is only reaching us now, was emitted pretty much right next to us (in galactic terms).
So it's been traveling for 14 billion years at the speed of light and is only reaching us right now, despite only having set off from right next door.
The standard explanation of how it's covered such a tiny distance begins with "expansion", which means the light has been swimming against the tide effectively and since that doesn't fit properly, it's augmented by inventing inflation which is basically a huge rush of Hubbly expansion at the outset, to increase the distance away from us before it began swimming towards us in accordance with Hubble's law which we now observe.
If we instead explain how it's covered such a tiny distance by saying that we are all departing the big bang at or near the speed of light because we are actually for example something like Hawking Radiation, then we don't need "Expansion" do we? Because the CMB is just the light that was emitted near parallel to us and has been traveling through space next to us all this time. So it's quite natural that it is only now reaching us. And then we don't need to invent inflation, do we, to make Hubble's law and the Big Bang fit?
And since it's been traveling so close to parallel all this time it seems natural that it should have such a low level of energy - unlike light emitted right next to us recently.
And then we have a natural reason for mass-energy equivalence don't we, because everything's moving at the speed of light anyway.
And then we have a natural reason for quantum theory don't we because if everything around us is moving nearly parallel at the speed of light then only its direction can change, not its speed so we would expect to find that if we impose a speed vector on objects which only have direction, their degrees of freedom will be over-specified and we won't be able to define their parameters all at once because they don't really exist.
And then it becomes obvious that "perceived speed" is simply an aggregation of how parallel the component parts of something are, so simple objects containing minimal component parts must travel at the speed light while compound things can move more slowly because they have component parts moving in different, changing directions around each other and their overall motion is the combination of the parts.
And then that would predict that a photon can't age.
And then everything seems to make a lot more sense because when we look out at the "Big Bang" in distant space and see it receding at the speed of light, well that's what we know it to be doing anyway so whoopdedoo who cares.
And because the universe is now just a set of paths in 4-dimensional space with no "speed", it should be described by a rotation group SO(3,1) and oh hang on haven't I seen that somewhere before, like the set of transformations in relativity?
But then we would all have to be made of light. So how do we design an experiment in which we bounce beams of appropriately formed light off each other itself at exceptionally low angles of incidence in order to prove that they do, to the surprise of almost the entire physics community, bounce off each other?
And how did we get in such a pickle inventing all this inflation and dark matter?
