I think you lost the context

> modern browsers warn about self-signed certificates the same as HTTP

So if I can read and understand those browser warning and am not a complete idiot, I will close the browser tab instead of proceed despite the warning. Which is the correct choice.

So now I cannot read the website at all.

Otherwise, if I do make the bad decision and accept the certificate, I don't know what will happen. But with HTTP, at least the browser says clearly that the site is unsafe.

So the fact that the website does have a certificate and serves HTTPS, as suggested in the GP, is completely irrelevant and useless.

> trust on first use has shown to be perfectly fine for SSH

If that is MY server or a server I trust/can verify. I don't know about you, but I never SSH into someone else's server and just blindly accept the keys. GitHub, for example, provides their SSH keys: https://docs.github.com/en/authentication/keeping-your-accou...