Privacy coins have privacy as a "feature", but that is not its purpose. It's purpose is to compete with Bitcoin, who, can at any time have privacy added to the base layer. The market decides what features are in Bitcoin. Altcoin's are only testnets for future Bitcoin features and will never replace it. Never.
These cryptos you've mentioned aren't private by default or their privacy features aren't reliable like Monero
Monero and Other Privacy Coins
https://lukesmith.xyz/articles/monero-and-other-privacy-coins/
Discussion
Privacy is not a "feature" it's a core component of cash in p2p digital "cash"
Because Bitcoin lacks privacy it's fungibility is weak and it is open to targeted censorship resistance
An encrypted base + L2 will always be better for privacy than one built on a transparent base
You're right Monero wont replace Bitcoin because it isn't trying to ossify or be transparent at it's base layer. They're two different projects.
"who can at any time have privacy added to the base layer."
lol
its never going to happen.
also, a technologies "purpose" is what it does.
not what *you think it's for.
OK. I know there's no use talking to my prior self