My opinion is utilitarian. It's actually in the interest of everyone, including NATO members, that they intervene.
You perceive your opinion to be utilitarian. I disagree with it, also as someone who in most aspects would consider himself a utilitarian.
NATO intervention is a level of escalation which isn't worth it in this case, and is also not in the nature nor charter of the organization (as it is a defensive alliance).
Russia will probably take Ukraine unless economic pressure and unexpectedly staunch resistance forces them to the table. However they will bleed for every square km they take, and from where I'm sitting I don't see how they can hope to hold it or prop up a puppet government. The Ukranians have shown they will reign absolute hell down upon the Russian invaders. And the economic actions from the US and Europe is going to cripple them.
There's no reason for NATO to intervene in order to cause Putin's Russia to blow itself apart internally.