I just feel like there isn’t a big enough crossover of people who both A.) know what it is and how it’s different from any other email provider and B.) don’t trust it simply because it’s encrypted.
The only thing ProtonMail does differently, functionally, is encrypt your data at rest, which while somewhat rare for an email provider to do, is extremely common for any other website or communication service to do.
Like somebody has to know what ProtonMail is and what it does enough so to not trust it, but somehow also not distrust iMessage, or WhatsApp, their banking site, etc.
Then you take that group of people, and cross them again with group C.) people who are responsible for the cybersecurity of any given website.
Like law of large numbers says that it’s plausible that this person exists out there, but is it enough for you to actually worry about using ProtonMail? So far at least, no.