Those who can afford it could pay their own hosting fees, and donations, governments, and philanthropic foundations could subsidize the cost of hosting for those who can't.

Most businesses could of course pay for their own hosting, and even now don't operate on "free" (ad-supported) hosting services.

So, yeah, I'm not really worried about the survival of the internet if unsolicited ads were banned. There's already a glut of content being created every day, and that's unlikely to be significantly reduced.