It is not accurate to say that "calls for anti-war can only be made to Russia". Ukraine could of course end the war today by surrendering. I'm not saying that that is good or bad, just that it's fact.
It seems to be heterodox to point out that the war could probably end immediately in some capacity other than total surrender by one of the combatants, which would necessarily involve a new status quo that does not comport with the pre-annexation territory lines. Musk was attacked endlessly for proposing such a thing.
I personally think the tragedy befalling the societies on both sides of this conflict are roughly on the same order in terms of magnitude, and that whatever we can do to end the senseless deaths of thousands of people should be done, regardless of where lines on maps end up. Our automatic and reflexive human drive for fairness and equity seems to be incompatible with this idea of letting an invader keep their ill-gotten territorial gains, preferring instead to continue slaughtering population on both sides in service of an old map.
It is not more or less tragic when a teenage Russian conscript's mother gets the news of her son's slaughter than it is when a Ukranian mother gets similar news of her own son after he has been forced into slavery in service of a status quo that no longer exists. I see everyone clamoring how this is "not our war" but neither is it that of those who are being forced at gunpoint into this violence, no matter what flag is on their arm.
If you believe, as I do, that the Ukranian people are a somewhat cohesive group with a distinct culture and identity that is worth preserving, the optimal strategy for preserving that culture and group into the future seems to me to take whatever actions possible that will preserve the lives of as many Ukrainians as possible, regardless of what nationality they are assigned by whoever controls the territory on which they live. I fear that they have chosen to trade numbers for sovereignty, which historically never works out very well when matched against an opponent with vastly more resources.
I want people (Ukrainians AND Russians) to stop being killed. Now. Today. All other considerations are secondary.