Not sure what you mean by 'secure'. If you send a person an email with ProtonMail, it defeats all the security that ProtonMail has (unless it's to another PM email). You should only rely on yourself for security. Start using PGP and demand that all your friends/relatives use PGP. Only sign in through Tor, use different emails for different services, etc.
You can't rely on a company to provide you security or privacy.
You can't rely on a company to provide you security or privacy.