"Resource consumption" in the parent comment refers to power efficiency, specifically GPU blits. That issue has not been ignored. I don't know what "CPU hog" refers to; the issue is not about CPU usage.
It's consuming ~20% CPU in idle on my machine (MacBook Pro Retina, 13-inch, Early 2015, 2.7 GHz Intel Core i5, 8 GB 1867 MHz DDR3, macOS Mojave 10.14.6)
That's not true. There was a roadmap posted yesterday and patches to begin to address the issue landed this week, including a new preference to opt into Core Animation. This is Markus' top priority at present. https://bugzilla.mozilla.org/show_bug.cgi?id=1429522
Source: I wrote the initial version of those patches, though I think Markus has basically rewritten them all at this point.
