Embrace the Madness
Morally, yea the Tau and certain craftworlds like Uthwa definitely have the high ground.
The only issue is that the Tau are slightly insignificant on the grand stage and the Eldar tend to be too removed and focused on the survival of their own species.
The Imperium get slotted into the good-guy club mostly for being the only “order” faction really getting shit done. The Tau and Craftworlders aren’t stopping Chaos, the Necron, or the Nids any time soon, at least not alone.
There’s a reason that one of the first things the Yenari did was resurrect G-Man.
The Imperium is sort of the big brutish bulwark against all the evil in the galaxy.