I've been of the opinion for the longest time that this is the main issue of NATO's eastward advance. Due to the immediate threat of nuclear war in case of any kind of NATO intervention against any near-peer force, NATO is limited to being a solely defensive alliance. While this is all well and good in terms of mutual security, it also forces all neighbouring countries to directly join NATO to gain any security benefits from them. This makes it, by nature, a bloated and constantly expanding organization.
It would have been much better to have willing ex-Warsaw pact countries in Eastern Europe form their own alliance that would provide mutual security without a direct nuclear capability. Something similar to the proposed interwar "Intermarium" alliance.
https://en.wikipedia.org/wiki/Intermarium
This could have been given mutual assurances by both Russia and NATO to have the nuclear umbrellas of both protect it from any nuclear strikes while simultaneously not expanding either alliance in these contested areas. It would have acted both as a buffer between Russia and NATO, and also allowed for a more active projection of power in the region in case of a crisis like this one. These countries are strong enough together to prevent any direct interference by either NATO or Russia in Eastern Europe.