Part of it is probably what determines what counts as “a religion.” My mind went to indigenous groups in the Americas, Australia, and Africa - thousands seems appropriate there!

Historically, religions as practiced on the ground were very syncretistic - like in the late medieval Muslim world, a Christian might carry a verse from the Koran as a charm or Muslim might visit a rabbi. Not to say that there wasn’t religious persecution and attempts by religious authorities to make sure that everyone was following the rules, but the species of religious fundamentalism we see today is a product of the 19th century and widespread literacy.

Even within a modern Protestant church of a specific denomination, there’s probably a mix of people who are universalists, into spiritualism, etc.

I don’t really think religions can be considered discrete in a way that one could report “there are X religions in the world.”