You are confusing the thing with the category of the thing.

Religion the category is only a few hundred years old. The things that fall under that category go back at least as far as Neanderthal times.

The conceptualization of religion as a category, is actually quite a bit older. The idea that it was created recently was, well, created recently.[1]

Casadio details it going back thousands of years across cultures.[2]

[1] https://plato.stanford.edu/entries/concept-religion/index.ht...

[2] https://api.pageplace.de/preview/DT0400.9780191045882_A29773...

it's an interesting point, and i don't think it can be resolved quite so neatly. to the people building such monuments, or writing such texts, the activity may have been closer to what we now refer to as "history" or "natural philosophy" (or even "civic infrastructure").

the fact that _now_, we have independent traditions referred to by those terms, and so categorize the ancient practices under "religion" is quite confusing, and it may be productive to make the distinction clear.

for a modern example, suppose we build a skyscraper in such a way that it lines up with, or reflects the setting sun on the solstice. we would regard this as "architecture", not "religion". i would be quite offended if, some thousand years from now, the aesthetic decision is dismissed as primitive superstition.

cf. "The Map is not the Territory"