Geopolitics is rarely, if ever, simple.
Yes, if NATO waded in in their own name, we'd all quite possibly be living out the film Threads right now. But that doesn't change the fact that, to all intents and purposes, it is NATO by proxy who are fighting Russia.
Again, most people can see that while the defence isn't being carried out in NATO's name, it's entirely reasonable to describe it as Ukraine/NATO. Especially in a flippant remark about Pat O'Sullivan.