No, they'll be relegated to the charitable internet, the advocacy internet, the nerdy obsessive internet, the public science internet, the FOSS internet, the public domain internet, and the piracy internet.
And whenever any of these groups come up with a project they want to do, they won't have to ramp it up to billion dollar scale in order not to be drowned out by a terrible and loud commercial product. There will be plenty of broke users looking for alternatives.
> This just means that 99.99% of the web will instantly disappear.
I think the only risk of this happening is if free alternatives get so generous and useful that the commercial internet tries to raise the price of bandwidth somehow, or of running a server in general, or alternatively by lobbying for expensive regulatory stuff to get governments to do their dirty work for them. The US seems like it's on the verge of state licensing of speech and journalism, and that sentiment is easily moved to any sort of internet hosting of any service.