Whether they have a ‘right’ to it or not is irrelevant. We live in the real world, and in the real world they can’t, anymore than Mexico or Canada could have joined the Warsaw Pact, or invite the Chinese to establish military bases on the US border.
And in reality, no-one is willing to die to join NATO. It’s not an ideal or a freedom, - it’s nothing. But it was a way for far-right Nationalists/Nazi’s to gain US funding and support, and then to gain power, and then to instigate the war with Russia that they had long desired.
And if it sounds crazy that the Ukranian far right would desire war with Russia - well, they’re fascists, they are crazy.
I’m not saying Russia’s actions are ethically correct, but if you look at it from a realist perspective, they are not only understandable but they were entirely predictable.
I don’t believe the Ukranian people wanted war with Russia, but a majority of people in West Ukraine did get caught up by fascist propaganda, and they trusted the far-right to lead them, and now the fascists have left their country in ruins.