Ask Lemmygrad

They absolutely could and would refuse to be dragged into a direct war over some backwater Eastern European states.

Firstly "Article 5" not some kind of automatic call to arms, it is sufficiently vague that the "aid" which it calls for to be provided by other alliance members (if that is even deemed necessary, which is another thing the article leaves open to interpretation) doesn't have to look like boots on the ground. More likely it would look exactly like what Ukraine is currently receiving: weapons, money and intel. It's why a lot of people have been saying that Ukraine is a de facto NATO member.

Secondly, it also wouldn't apply if a NATO state actually was the one who attacked first, which would arguably be the case if they chose to get involved in Ukraine.

And lastly, all NATO members are not equal. The Eastern Europeans may like to believe they are equal and that the entire West would come to their defense but that is highly unlikely. Western Europeans have no desire to go fight and die for Eastern Europeans and neither do Americans if it means a risk of taking significant casualties. Oh sure if the enemy was a sufficiently weak country then they would all jump at the opportunity, but against a peer adversary like Russia you will see most of NATO chicken out finding excuse after excuse for not having to send their own soldiers.

So yes, if the disincentinve is strong enough, states can absolutely refuse to honor any treaty requirement which is against their interest. They will simply apply a "creative interpretation" of the treaty or claim extenuating circumstances. Treaties aren't magic, they don't bind sovereign states unless said states want to be bound by them. Of course Europe is vassalized to the US so they don't really have the ability to make a sovereign choice; the choice will be made for them in Washington.