As one of the crackpots, the primary problem I see is that this expansion is in comparison to a stable speed of light, which would make lightspeed the actual metric of space.
When the redshift of distant galaxies was first observed, there were two initial assumptions. The sources are moving away, thus doppler shift. Or the light was being interfered with in some way, aka, "tired light." Which, as this article states, was dismissed because the light from distant sources was otherwise clear.
Yet it was realized early on that as redshift seems to increase proportional to distance in all directions, it makes us appear to be at the center of the universe.
Since it seemed doubtful the solar system happens to be at the exact center of the entire universe, it was argued that space itself must be expanding, such that every point would appear as the center.
An analogy of this is an inchworm, as light, crawling on an expanding balloon, of space.
Which has long raised a basic conceptual issue, at least to me, one lone skeptic/crackpot;
The argument used is that spacetime, as physical explanation for the math of Special Relativity, would be the reason why space itself can expand. Yet this seems to totally ignore the central premise of SR, that the speed of light remains constant to the frame in which it's being measured. If intergalactic light is being redshifted, obviously it isn't constant to intergalactic space. If it were, the speed of light would have to increase, as space expands. Yet the reason for redshift is supposedly that the light takes longer to cross, as the universe expands. The inchworm goes the same rate, while the balloon expands under it.
Yet that means the expansion is being measured in terms of the speed of light. As Einstein said, "Space is what you measure with a ruler." And in this case/theory, the otherwise stable speed of light remains the ruler. It is the denominator, making the expansion the numerator, as increasing distance in the otherwise stable metric defined by the speed of light.
If the speed were the numerator, than it would be a tired light theory.
I happened to come across a paper some years ago;
https://fqxi.org/data/forum-attachments/2008CChristov_WaveMotion_45_154_EvolutionWavePackets.pdf
Making the point that while single spectrum light only redshifts due to doppler effect, the recession of the source, relative to the receiver, multispectrum light "packets" will redshift due to distance alone, because the higher frequencies dissipate faster.
Given we are at the center of our point of view, this optical effect would be something worth looking into.
Though it does open a much larger Pandora's Box for physics, as this would mean we are sampling a wave front, not observing individual photons traveling billions of years. Which would suggest the quantization of light is a function of the ability to absorb and thus measure it, rather than of the light itself. The information we can extract is not synonymous with the underlaying energy and that runs up against a significant information based, "It from bit," view of physical reality.
Which will continue chasing after its strings and algorithms for the foreseeable future, even if they only seem to go in circles.
