Let us look at the temperature issue first.
https://observatoiredeparis.psl.eu/taking-the-temperature-of-the-universe.html
The article acknowledges that these temperature calculations are based on computer models.
If the models are wrong the temperatures are wrong.
This article suggests the “delayed light curve” analysis is ultimately dependent on the “red shift”—yet again.
https://www.mdpi.com/2075-4434/13/3/55
What I have noticed with much of modern cosmology is that they tend to start with a conclusion (the expanding universe) and then tend to use computer models that support it and reject as “anomalous” those that reject it.
The ground is not as solid as it may appear.
The conclusion in this case is also supported by a preponderance of the evidence. But yes, there is always the danger of deer-in-headlights if you accept a certain thing long enough. Is it called confirmation bias?
In regards to dark matter and dark energy, by the way, I think most accept that they are just running theories for now. They’re just terms for observable things that we can’t explain yet. One of the leading proposals to explain dark matter is in fact that it doesn’t exist at all. It’s called MOND (modified Newtonian dynamics).