This is highly impractical, and possibly even detrimental to your privacy/security. For one, most people are simple not qualified for such an undertaking, but that's probably not the biggest problem. It's the people who may think that they are qualified and may follow your advice and self-host. Some exceptions aside, almost nobody should put anything up on the internet unless they've done it in some professional capacity before. It's a fallacy to think that an average Joe can push a button and replace Google by paying 10-20 bucks a month to a cloud provider. For most people, a better solution is to use services like signal or protonmail/tutanota (at least until end-to-end email matures, at which point other big players will support it too)