But, why is time considered valid? If the 4e archons, for example, had come first, then everyone's arguements in this thread would flip. 4e archons would be the "true" archons and the earlier edition ones would be bad changes.

In other words, the criteria has absolutely nothing to do with the ideas themselves, but rather, which one came first. The quality of the idea doesn't matter. It could be great, it could be terrible, but, since it came first, it cannot be changed.
How can that be justified as a valid criticism? Yup, the Great Wheel came first. Absolutely. No one is arguing that it didn't. Does that automatically make it superior to the Astral Sea? Why?
Now, you can certainly dislike the Astral Sea (and I'm just picking one example, feel free to choose your own). And you can make all sorts of arguments about why it is a bad idea - it cheapens the ideas of distinct planes, it makes the planes less interesting, I just don't like it. Fair enough. But, saying the Astral Sea is bad because it comes after the Great Wheel doesn't seem like a particularly convincing argument.