It was depending on Web Components v0 stuff that was enabled in Chrome before it was ready.

You may find that the component does still work in Firefox (which never implemented the stuff that Chrome eventually removed, and for which Polymer included polyfills).

Also, my hobby horse: HTML imports were removed, not just deprecated (or depreciated). Two (three!) very different things.

Decimated?

… and that word alone means two very different things because of incorrect metaphorical usage! (Its original sense, now rare, was killing one tenth of a group of people, and so metaphorically the destruction of a tenth of something; the typical meaning now refers to a much more drastic reduction than ⅒, very commonly almost complete.)

If the pages worked in Safari and Firefox then they would still work in Chrome now. The only pages that would have broken are those that didn't load the polyfills at all.

It was a bad situation which I hope is never repeated.