Progressive enhancement
Building so the page works with HTML alone, then adding CSS and JavaScript as improvements rather than as requirements.
The argument is not nostalgia. Scripts fail for ordinary reasons — a timeout, a blocked domain, a parse error in one bundle — and a form that submits without JavaScript keeps working through all of them, while one that does not becomes a dead rectangle.
It has quietly become an AI question too. Crawlers, feed readers, and agents read structure, and a page whose content only exists after a script has run is a page they see as empty. What survives without JavaScript is roughly what survives being read by a machine.
In practice it is a sequence, not a doctrine: make it work, then make it pleasant. A link that navigates and is then intercepted for a smoother transition costs nothing extra and degrades to a link.