I've been wondering for years why NATO kept moving its border eastward. I do think it's complicated. The former eastern bloc countries pushed pretty hard for it, for the reason we see happening with Ukraine. But Putin isn't an unknown. He hammered Grozny and Aleppo the way he seems to want to hammer Ukrainian cities. So a little foresight would have been nice. I don't think it helped that the state department was gutted for 4 years but I also doubt Hillary would have said no to further NATO expansion.
In the modern world though, we may just have to accept that countries have spheres of influence. Let Europe be Europe, let the former Soviet countries do whatever they do, and let China have Taiwan.
I love microchips (the reason we would fight for Taiwan) but not enough for a war with China.