Yes, I'm a fan of SimpleX. But if you care about privacy defaults matter. How many use tor/i2p or even VPNs? They are inaccessible to the average person because of ignorance or lack the time to learn (not necessarily because they wouldn't like to be private). It's more friction between them and privacy.

Look at BTC, LTC, Zcash. All have optional privacy, but no one uses them that way.

I wouldn't be so sure.

Unless Bitcoin hardforks (wont happen. immutability is a major value prop) to improve privacy on the level of Monero, Monero will always be useful because of it's unique L1 tradeoffs it offers. You can gain privacy on L2s but take on different tradeoffs from either Bitcoin or Monero.

Bitcoiners always bring up network effects, but conveniently ignore that Monero has the largest network effect for privacy coins. And it is only growing over time on the darknet and will most likely displace Bitcoin (chosen by a free market and adversarial environment where these things matter and are put to the test).

So far, any possible L2 privacy improvements you lose custody (fedimints), non interactivity (lightning), permissionlessness (liquid), change mining incentives (drivechains). Other trade offs exist with each one but those are some major ones.

The wise know there are no perfect solutions, only tradeoffs.