While the 'experts' arguments may be pertinent to 1950, I'd argue, in this day and age of perpetual peace amongst European neighbors, it shouldn't matter if a Nato nation is bordering a non-Nato nation since neither would be contemplating war with each other. Russia is so large, it's not like they have to expand to accommodate a population bursting at the seams or have experienced such an increase in exports their existing ports can no longer handle the burden so they have to steal their neighbors’ ports. Even if they do take Ukraine's ports, Turkey is still holding the gateway keys to the Mediterranean via the Straits. And, if they do take Ukraine, that puts them solidly against a REAL Nato nation - Poland.
So if distance from Nato is the objective, invading Ukraine is a weird way to go about it. Making this a senseless conflict and a waste of Russian resources. Putin's talking out of both sides of his mouth, claiming to be fighting 'nazis and nationalists' in Ukraine, while acting like a nazi and enshrining Russian nationalism out of the other side.
It's incredulous that an argument would be made that the US and/or Nato are causative. Blame the information age, but desire for freedom is going to overtake every nation that doesn't have it, including Russia, and invading Ukraine isn't going to stop that desire.