No? Virtually nobody uses Protonmail. If the only thing between encrypted email and no encrypted email was a single provider that implemented PGP, we'd have had universal encrypted email in 1999.
(I'm stipulating that anything Protonmail does actually, you know, works. I have no idea if it does. Why bother? Encrypted email isn't going anywhere. The track record on things like this is quite bad.)
In 99, webmail providers were nearly all using squirrelmail or some self-invented thing and people were using offline mail clients, where GPG/PGG could have been an option. The terminals were behind, cloud computing ahead, and everyone knew your stuff is gone if your are careless and reinstall your computer, since POP3 was still a common thing. (Unlike IMAP, POP is usually used in a mode where no copies are left on the server, so the mails only exist where you pulled them down to.)
The big difference, however, that the world wasn't yet spying on every drop of text you made, and that is why email encryption didn't take off: there was no real need.
Unfortunately, the cloud and web "revolution" happened before people realized they should encrypt _before_ moving back to centralized services and now it seems to be a lost cause.
No. I don't know if it's a generational thing, but people on message boards today seem pretty convinced that Snowden invented concern over dragnet encryption. Get a copy of Applied Cryptography and thumb through it; it's shot through with the mindset that NSA (specifically: NSA) is reading all your mail. The 1990s were the decade of the cipherpunks, the Clipper Chip, the crypto wars, Echelon, and the hacker crackdown. More people encrypted their email then than do now.
But NSA - I really hope - doesn't sell your data for profit to insurance and medical companies, so there's a difference. If NSA picks up something serious about you, you're in deep trouble, but the current data sniffer companies can make your life really hard without you even realizing it.
I'm not advocating plaintext email. I'm advocating for no email. But since it'll be 10-15 years before email takes its place alongside ICQ among protocols normal people never use, in the meantime, the right solution is to keep email banal, and keep sensitive stuff on secure messaging protocols.
So what, it's all or nothing for you? Even if there is an easy to use solution that you can set someone up with in about 10 minutes, that's absolutely valueless because it means that less than 100% of messages will use it?
I'm a little concerned that the emerging consensus in question may be led by you, as you are a famous information security expert and people take your concerns and views very seriously. When you mention your view about this here or on Twitter, lots of people quarrel with you about it (some of them engaging with it seriously). A number of people have been persuaded by your arguments but a number of people keep strongly disagreeing.
But it's possible that more people agree with you and fewer disagree in contexts where people have more information security expertise or where more of them work on it professionally.
There is a presentation[1] by grugq on how to communicate securely. Using gpg with email is hard. Anecdotally, people reply in cleartext quoting the encrypted message. If you can train and test your co-conspirators before sending them incriminating evidence about yourself, maybe it can be done. But mistakes happen so often, people who have secrets that can get them killed or jailed for a long time just switched to Signal. That's what tptacek means.
(I'm stipulating that anything Protonmail does actually, you know, works. I have no idea if it does. Why bother? Encrypted email isn't going anywhere. The track record on things like this is quite bad.)