An argument that our universe is a giant causal loop
You're assuming that a causeless cause is possible, simply on the basis that anything exists -- this does nothing to refute the claim that all events must have causes, thus that the universe must be a causal loop.
The fact that anything exists still follows a causal loop model, where causal loops as a whole are not create and do not have a first cause - they simply exist. But causality still obeys a logical consistency within the loop (i.e. no event without a cause). So the fact that anything exists cannot necessarily be attributed to a causeless cause as you suggest, and shows that there's still an important distinction to be made between infinite vs finite causality that cannot be waived off as a false dichotomy.
So what you may view as a causeless cause is what I view as the causal loop as a whole -- which is above causality itself.