If religion stuck to abstract spiritual concepts then that's possibly true. But religious teachings move beyond this and assert facts. Like the earth is X years old, evolution is fake, there is an afterlife, if you believe in god you will be rewarded in X way. Once you start asserting facts, and especially asserting cause and effect then your belief system is in principle testable and therefore subject to scienrific proof. So you skirt around the issue and say that anti theists act in bad faith by expecting religion to satisfy scientific principles.

Consider an analogous belief system: that of Santa Claus. Certain facts are asserted: there's a big fat guy in a sleigh who lives at the north pole and rewards kids on Xmas eve who believe in him. In principle everything that is asserted there is testable. But when you start doing so the inability to find his workshop is conveniently brushed away by saying things like he uses magic to hide his location. Or if I set up a surveillance system to catch him on Xmas eve when he comes to my house to bring me presents then when he doesn't come its because I didn't believe hard enough in him. There's always some reason for the complete lack of evidence. So it is with religion. If I just "believe harder" then god will reveal himself to me and I'll get the proof I need.