This was already answered but to be clear: ”doing something” and ”invoking article 5” is like the difference between saying ”asshole” in traffic vs rallying your friends to murder the driver’s family.
One could argue NATO countries should respond stronger to hybrid and clandestine warfare. Right now, we see a lot of ”angry letters”. But, it’s not clear eye for an eye is a strategically sound response, partly because it legitimizes the methods, and partly because it escalates tensions towards a war that nobody wants. Israel for instance takes an entirely different stance, basically retaliating with maximum force to deter the enemy (similar to punching the ”school bully” so hard, just once, that he stops). I don’t claim to be a diplomatic expert, but it’s worth noting that Israel is currently engaged in several major wars and conflicts, and tensions have grown.
Is there a threshold anywhere in the NATO treaty that I'm unaware of?
In other words, and following Eastern-European logic (which, trust me, helps in cases like this one, I'm from Eastern Europe myself), had Russia really attacked any NATO countries you and me both wouldn't be in here having this conversation over the internet.