My headlights were very deeply scratched and crazed when I bought my car a couple of months ago, so much so that I thought they'd never be clear again.
However, a couple of days (yes, days) spent with successively finer grades of wet and dry and followed up with Maguires metal polish, applied with an electric drill fitted with a foam disk and they were a universal and complete opaque white. Wet them down tho and they didn’t look too bad. So I dried them off, hit them with some compressed air and they looked ok ish!
But then I remembered those YouTube wood-work videos I've watched where they sand down a bit of timber filled with resin. After they sand the resin it's opaque and then they polish the whole thing with wax to get a mirror finish. It worked for me too! I decided to call it quits with the sanding and polishing and finished the lenses off with a rattle can clear coat.
They're not perfect by any means, you don't have to look too carefully at the finished result to see the imperfections but they're a dam sight better than they were.