I can see that our current understanding of light is a problem for the young universe view, but I can also see that it is just as problematic for old universe views.
In what way is our understanding of light a problem for an old universe view?
For me, the Horizon problem by itself is a major clue that we don't actually understand how light and radiation behaves. Also indicative of how naive we are, are the many unsupported placeholder theories like dark matter, dark energy, Cosmological principle, etc. Bottom line, I'm not convinced that we have light and time properly understood, specially in the bigger scale.
The Galactic center, about 25,000 ly. Problem for YEC? Yes, it's about 4x farther than we should be able to see. Problem for old universe? No.
Sn1987a distance 167,000+ly (measured by trigonometry.) Problem for YEC? Yes, it's about 28x farther than we should be able to see. Problem for old universe? No.
Andromeda distance 2.4 million ly. Problem for YEC? Yes. It's about 400x farther than we should be able to see. Problem for old universe? No.
Centaurus A distance 12 million ly. Problem for YEC? Yes. It's about 2000x farther than we should be able to see. Problem for old universe? No.
How about a supernova measured by standard candle techniques at 6 billion light years from Earth. Is that a problem for YEC? Yes, it's a 1,000,000x farther than we should be able to see. Is it a problem for an old universe? No.
You consider this "just as problematic?" Hmmmmm.......
All of the things you mention are problems for the Big Bang; expansion of space; formation of galaxies ..... but none of them are issues for an old universe out to billions of light years.... hundreds of thousands of times farther than we should be able to see.
I see no equivalence at all in the scale of the problem..... YEC is refuted a million times over before an old universe even begins to have issues.
So should I trust modern day priests who think they "got it down", or the "great high-priest" who has ascended into heaven?
It is not my place to tell you what to believe or why.
Since you trust what you understand best, are you saying that you understand light and the old universe better, than what Christ has clearly said about the "beginning"?
Edit: Accidentally posted prematurely.....
I'm saying I understand the physics a lot better than I do ancient Hebrew. Our ability to see distant objects and the time it takes light to reach Earth from those objects is much more simple direct evidence far less subject to errors of human interpretation than the Bible.
For example, when I pointed out a discrepancy with regard to Adam and Eve dying on the "very day" they ate the forbidden fruit, I was treated to a lecture on hair splitting semantics, ancient Hebrew verb tenses, and a bunch of apologetics from the very people who demand I should read the text literally. When I used "kinds" as stated in Leviticus, I was told the list of kinds in that reference was "conjured up" (yes, those are the exact words) by the translators. Yet, these were the dietary laws the Jews were expected to obey.