To me it seems as though it is more so a political change not so much a
change done for some technical improvement (there aren't any).
Mozilla is closer and closer with google, as evidenced by making
telemetry opt-out rather than opt-in [1] and all the "safe" browsing and
downloading "features" which sends a list and hashes of all the files
you download to google for inspection.
This is going to break a variety of beloved addons as the new method
can't support heavy modification of firefox.
[1] as if anyone WANTS to be spied on, the average user has no idea what
telemetry is and or would believe mozillas bullshit reasoning of "we do
this to make the browser better, trust us!" I myself have noticed it
mysteriously turned back on a variety of times similar to windows not to
mention the annoying practice of allowing addons to randomly open
windows every update without permission (10 addons 10 windows to inform
of random changes no one cares about, and now my ISP knows what addons I
use as it loads their websites - yay)
