Religion isn't flawed, people are.
1) It appeals to people's romantic notion that there actually is a really good religion out there. The reason they haven't found it yet isn't that none exists, it's that all the ones they've tried so far have been screwed up by humans. This "restoration of the recruitee's hopes that an all-powerful guiding hand exists"... that's very very useful, because the euphoria they feel from this makes them more pliable.
2) It suggests that scriptural inerancy may be wrong. (that is, it takes a universalist view, which means that the various texts that exist, which directly contradict each other.... those contradictions were added by humans) People who are searching for a "more modern" religion are likely to have come to this conclusion already, and the fact that Late Antiquity religions still heavily suggest that their religious texts are inerrant allows you to present a refreshing change.