Doesn't matter in the larger scheme of things, unless Hotmail and Gmail implement it too. Also: easy migration paths that includes secure key transfers.
Average Joe simply isn't technical or motivated enough to do it on their own.
Absolutely! There's nothing wrong with Protonmail's offering, it's just that the other players' dominance will keep that offering from becoming mainstream.
If Gmail started supporting GPG then pretty much everyone would implement it.
Google would not give the keys to the users, so they would still technically be able to decrypt your emails.
I don't think they would implement a security feature that is based on user password (in protonmail you loose your mails if you loose your password).
That blog's author also suffers from obvious mental issues if you look at any of the articles on it.
Nearly everything he says there is not substantiated. The links don't actually support his arguments, and in fact disprove them in some cases.
In one case he accused Disroot of DDoSing his crappy blog because they wouldn't deny some claim he made that they probably didn't even know about. He used to post it in /r/privacytoolsio until we banned him for low quality posting.. That article is here: https://privacy-watchdog.io/the-truth-about-disroot-org/
Average Joe simply isn't technical or motivated enough to do it on their own.