There aren't that many archeological artifacts even from North India in the Vedic age that "proves the existence of religion" so to speak
Yet we all know that the Gangetic plain circa 7th cen BCE was profoundly religious
Not as much from the archeological record
It's foolish to infer much about the culture of a certain epoch solely from archeological record
The Hindu religion was extremely dominant. And you learn this through the literary sources
The two epics, the numerous purANas, the sutra literature of the various darshanas - all dating to that period of supposed "Buddhist dominance"
IVC culture - ample archeological record. Fabulous ruins. Yet no literature that speaks to us. Undeciphered seals
Vedic culture - relatively poor archeological record. yet literature is massive!
As though the coming of the Aryans was a "backward" step of sorts.
Romila Thapar says in so many words in her book!
If durability of ideas is the true test of a civilization, then the Vedic epoch beats IVC hands down
Ideas matter more than ruins
But the culture of the itinerant, materially poor seers of the Vedic period continues to exert an influence