That said, watching the Comac C919 shitshow (14 years and still not in revenue service, and this is for a 737/A320 clone), I'm not holding my breath.

This is true, but this is also a command economy. They can do that for a long time. At least 10 more years with gov't support. They'll get there eventually, plus the order book is essentially infinitely large because gov't will immediately force all domestic carriers to cancel foreign orders and only buy Comac C919. I am guessing it can handle 100% of internal flights (size / distance / etc.)