I took a very bold decision and built a new version of the site using Astro https://astro.build/. It was HTML-first. Javascript existed, in web components, but only to progressively-enhance a website that worked perfectly fine without it.

My logic was thus:

1. This is a public service
2. It should work on every machine possible
3. It should work when connections are poor
4. The forms must never lose data once it is entered

…

The results? When we launched, the number of people completing the form doubled. The analytics people didn’t even know where these users were coming from. Of course, your javascript-based analytics package doesn’t see the users you are bouncing because of javascript failures. It was a flood! We also saw my “keep a backend session, never lose user data” approach pay off. In one case, someone completed a form a month after starting it.