Being private AND offchain is definitely ideal for privacy. That is true.
Monero gets L2s with FCMP++ in a year or so.

"There is no reason to use a different monetary token & deal with exchange costs & risks & lack of acceptance."

What? You deal with exchange costs and risks in lightning, liquid, and ecash too. You also deal with the additional cost of force closure fees in lightning, and rug risk with ecash. Liquid rug is also possible too just much less likely (privacy sucks though. doesn't hide sender/receiver and abysmal anon set).

https://boltz.exchange/