Correct. Unfortunately, what you've just described is a gaming console rather than a PC. This problem fundamentally undermines the appeal of PC gaming in a significant way, imo.

> my main concern is for the “long tail” of the web—there's lots of vital information only available on random university/personal websites last updated before 2005

It's a strong argument for me because I run a lot of old webpages that continue to 'just work', as well as regularly getting value out of other people's old pages. HTML and JS have always been backwards compatible so far, or at least close enough that you get away with slapping a TLS certificate onto the webserver

But I also see that we can't keep support for every old thing indefinitely. See Flash. People make emulators like Ruffle that work impressively well to play a nostalgic game or use a website on the Internet Archive whose main menu (guilty as charged) was a Flash widget. Is that the way we should go with this, emulators? Or a dedicated browser that still gets security updates, but is intended to only view old documents, the way that we see slide film material today? Or some other way?