Secure email is snake oil; no amount of cruft can make it both reasonable secure and useful (as in federated). Other protocols better fill that space because they were designed for security needs.
I wouldn’t call secure email snake oil: it meets some of the characteristics, but not all. “Snake oil” implies at least in part inefficacy and deceptive marketing; yet secure email is possible, though there are typically rather severe caveats (mostly around the question of which parts are being encrypted, and usability).
What is actually snake oil, and distressingly rarely realised as such, is first-party end-to-end encryption. That’s what sodality2 is actually talking about. And when you stop and consider it in this light, you realise that the significant majority of stuff that’s advertised as having E2EE is first-party and thus, to put it mildly, not robust.
I agree that I wouldn't use Protonmail if Signal was an option, but there are many situations where Signal isn't an option (eg. transactional email, people who don't use signal). In those contexts it's still better to use encrypted mail rather than ad-supported mail (eg. gmail, outlook), or even commercial mail (eg. fastmail), which are both unencrypted.
End to end secure email definitely is, I agree. No matter what you have to trust the server. (Maybe a Tor-based email system would be better, where each user is their own server? reminds me of `cables`).
If you do trust the server then it can be acceptably secure.
What is actually snake oil, and distressingly rarely realised as such, is first-party end-to-end encryption. That’s what sodality2 is actually talking about. And when you stop and consider it in this light, you realise that the significant majority of stuff that’s advertised as having E2EE is first-party and thus, to put it mildly, not robust.
In the context of email, here’s Fastmail’s take on it: https://fastmail.blog/advanced/why-we-dont-offer-pgp/.