There are phases tossed around like "Lest we Forget" or "Never Again". But when Russia invaded Ukraine, we have effectively done the opposite (or very nearly).
I read these two sentences as being at odds with each other.
When I hear "never again", I take it to mean that we should remember the cost and horrors of war, and we shouldn't enter into another war lightly.
We cannot allow genocidal wars to be pressed in the modern world.
Morally I agree. Practically, it's a harder case to make. We're currently ignoring genocide in Yemen, and the plight of the Rohingya, and Uyghurs.
When we tried to stop the Rwandan genocide, and failed miserably.
I doubt we'd do much better in Ukraine. Worse, it would give Putin an excuse to use nukes.