what exactly do you think is going to happen if article 5 gets invoked? did America's current Special Military Operation not make it clear that missiles alone don't win wars, and that there's fuck all you can do when the other side yeets their missiles at you in return?
also, a friendly reminder that all willing parties are free to go fight Russia right now. https://ildu.mil.gov.ua/
It will lead to a gradual escalation, probably air spaces closed over Kaliningrad, Belarus and Ukraine for Russian planes and army mobilization towards the eastern flank of NATO in the first steps.
Sufficient assistance can be given to the Ukrainians without deploying troops to the battlefield so that the Russians are pushed out completely. Losing Crimea would be Putin's death knell.
NATO does not need to win a war. They just need to hurt Russia bad enough Ukraine wins.
Invoking Article 5 and winning a war are entirely separate operations.
In terms of https://en.wikipedia.org/wiki/Weinberger_Doctrine if article 5 was invoked, one could set much clearer victory conditions - chase Russia back into Russia. Maybe arrest Putin war crimes or something.
It would still be extremely unpleasant, painful and expensive, of course; winning an exchange of blows still means taking a load of punches to the face. So the true winner would be China.
Maybe like destruction of Russian military command structure sparing just the silo based nuclear force?