The universe appears "old", but it is still less than 10,000 years old

[Zen Badger]

Even if you wish to tout it as a convention it doesn't change the fact that it still takes light a finite time to travel a given distance. Despit all of staplers protestations to the contrary.

I think I disagree. How do you measure the time it takes light to travel from A to B, and how do you define the time interval delta T which it took? You will implicitly use the "isotropic" synchronization convention to do it. The point is not that this is a deep physical difference, it's just that light travel times for one-way trips are a convention dependent quantity.

But that's not my point.

Regardless of what convention you might wish to use.
Independent of any measurement, it still takes light time to traverse distance.
It is never instantaneous.