No knows the final result of any geopolitical decision, even the pacifists.

One geopolitical reason for outside countries not to put boots on the Ukrainian ground is that the Russian culture needs to shed its domineering- other-ethnic-groups mentality. If Russia is pushed out of Ukraine mostly by Ukrainian people, this Russian attitude is more likely to change than if the west starts putting in real soldiers. There are other reasons, of course. Political suicide is credible, but this could change.