Funny, I feel the opposite. My email is way too important to be left to a free service. I pay for Fastmail, and they do a great job. If I were to have a problem, they provide support.
I greatly prefer that model to letting Google mine my email. As others have said, you are not Google's customers with email, their advertisers are.
Actually, you're not paying for e-mail. Every common OS nowadays is equipped to be able to send mail, so paying someone else for that would indeed be not-so-great.
You are paying for the interface. He wrote software and probably devoted many hours, and that's what you are using. I can imagine you still say it's not worth paying for, especially since there are even entire operating systems that are free (of cost), but I think it's reasonable to ask. If it works better than Gmail, I can see why many would pay and switch. You may not, that's your decision of course :)
How about paying a one time license fee and install the app on your own server/get your own Mailgun account etc. That way you have more control over your data.