I have not yet fully analyzed Babilonia, but waxwing is a genius, so I am already excited.

What is standing in the way to it seeing widespread adoption on mainnet? Also: when trustless casino?

Gamblers care about two things that affect their bottom line: The trustworthiness of the house, and the house edge. I don't think there's a shortage of trustworthy casinos (they practically print money).

On chain fees cut against the profitability for trustless Bitcoin gambling at scale, so maybe Ark is a necessary prerequisite. I wasn't around for SatoshiDice when it existed, but I'm surprised that concept died out instead of evolving.