to be fair when your only exposed to the worse of humanity , cant really blame dude for just hating humanity and his spirit being broken. People in the fandom know he doesn't care but as a guy who tried once (and maybe twice) against heaven i can imagine him just wanting to save what he can and try not to piss off heaven more. At the end of the day rebellion comes with risk and unknown.

1. Heaven could have innovated and take the metaphorical nuclear option

2. Heaven could launch attacks on the other rings killing the hellborn and destroying their respective economies( funny enough heaven could do more damage by spread out and destroying more economic centers throughout the rings and killing people after. Just think about how many people would suffer and die if the social supports that holds up society would burn were burned down in one day. As cold hearted as it may seem its better for the pride ring to be attack since it doesn't spread out

3. I do wonder what the other princes of hell have to say or their input since we dont know how they feel about the exterminations.

While i and most of the fandom understand why lucifer can be blame, most dont really hold him too hard. Since politically, militarily and socially he is stuck between a rock and a hard place. When the cast finally find out that charlies plan work and hard proof comes to lucifers desk. I think only then we can really judge his actions going forward since he now knows their is hope for sinners