> I wonder where 'pointless slurry' is meant on the scale of justifications or rationalizations of war?

“pointless” = “without decent justification/rationalization", AFAICT, and “slurry” is about conditions, not justification.

> Maybe more favorably than 'quagmire'

“Slurry” seems to indicate a similar assessment of condition to “quagmire”, but maybe with less implication of stickiness? “Quagmire” doesn’t seem to be address justification, its orthogonal.

A quagmire is something you get stuck in, it implies a sort of stagnation. A slurry is what happens when you really stir up the shit.