I think you are arguing against a strawman.

No one is saying that trade makes war impossible-- but every bit of trade is an additional incentive to not start war, especially if it affects a broad slice of the population directly (=> the average German would be much more affected from losing car exports than the average Russian from lower gas exports).

Regarding Russia:

I believe that the main mistake on the western side was underestimating Russias imperialistic ambitions combined with the almost existential risk that a western aligned, economically successful Ukraine would have been for the current regime: Russian citizens getting overtaken economically by former compatriots makes it much harder to keep the kleptocracy running; Poland is one thing, but the same happening with the Ukraine would have hit much closer.

But regardless, I'm highly confident that Russia/Putin would have decided against the war with the benefit of hindsight.

You could even argue that insufficient economical consequences (from the Europeans-- basically the other, necessary side of the peace-by-trade playbook) after the 2014 annexation were a big factor in encouraging the war in the first place.