The researchers responsibly disclosed FROST to Google, Apple, and Mozilla before publishing. The responses are worth reading carefully:

• Google said it does not consider browser fingerprinting to be a security vulnerability.

• Apple described the attack as “currently out of scope,” with possible mitigations in the future.

• Mozilla acknowledged the findings but has not implemented any fix.

In other words, the three companies that ship some of the world’s most-used browsers have collectively said “ok, not my concern”.

This isn't entirely true. Apple and Google said "piss off", but Firefox acknowledged the issue, but don't yet have a solution, which doesn't mean they aren't working on one. It is bad, though, that they haven't come up with something during the responsible disclosure timeline.