This is a very valid point. The best answers I have is that these things are not binary. There was no NATO that caused WW1 or 2. We are talking about a democratic country who peacefully disarmed their nuclear deterrent in exchange for guarantees of security from UK, US and Russia. I can’t say I am an expert, but do those guarantees not still stand? We are talking about a country who aspired - and even wrote into their constitution - to join NATO.
The only difference between the current situation and Hitler is that the latter didn’t have nukes. It’s unfortunate that we live in a world where mutually assured destruction is a possibility, but it is. The question is, is Putin really prepared to destroy the world (since I’m damn sure they would be the ones to make the first strike if it happened)? And would the Russian people and military let him? Until troops are marching on Moscow, I can’t see it happening. As long as NATO was clear about retaking Ukraine (and maybe Belarus while we are there), there is no reason to escalate.
My other idea was to enact a no-fly zone over Ukraine. Putin publicly claims that this is a special military operation, focused on the Donbas. With that in mind, a no-fly zone over the rest of Ukraine (ie Kyiv) should not interfere with his plans. Ukraine has the right to request their airspace be protected.
In practice, this would either mean Putin ceding that this is a full invasion, or sacrificing air operations - which would give the Ukrainians a much better fighting chance, if nothing else.