> if it ever gained popularity it wouldn't stay regular
This. Utility and purity always pull in opposite directions.
I see those boutique little (programming) languages written by amateur language designers with exotic type systems or “everything is an X” philosophies, and my reaction is to assume that they are useless for anything past toys and experiments.
I know useful language features have been born in that world and then eventually bolted onto mutt languages like Java and Python, but that suits me just fine.