We need to take a sober look at the real state of affairs today. Ukraine is quite successful in coping with the Russian invasion without being a member of the collective security system. In other words, Ukraine now convincingly answers the above question.
The second point is about realities. For any country, joining NATO means a long procedure. It is primarily about bureaucracy — an invitation, then a plan for greater NATO membership, annual national programmes, and so on. But what if something suddenly changes and Ukraine gets an immediate invitation, and then the next day our flag is raised in Brussels? I would say, yes, it is possible.
