What are the options? The war in Ukraine is a land war of attrition. They need more soldiers. Many Ukraninians evade military service and are instead refugees in the EU.
Sending NATO troops to do their work seems strange, especially considering that we are talking about a relatively small piece of land in Eastern Ukraine. And no, Putin will not go for Lisboa if he still does not manage to occupy the whole of Donetsk.
Do you blame NATO for not recapturing North Korea?