It's absolutely not a responsibility to continue or escalate a conflict when it is hopeless, it's suicidally stupid.It’s not even a decision. It is a responsibility. We disarmed them and promised to defend them. We have no choice. The other option is to give them their nukes back.
Their defense would have collapsed in 6 weeks without our support, what we are doing has been effective. So until Ukraine decides to surrender, nato is on the hook for their support.