The alternative to NATO expansion was transferring European defense to the EU.

Or having a bunch of EU nations extremely vulnerable to Russian influence.

I’m very glad it’s NATO, and not the “EU Supreme Command” defending the Continent. Russia and Ukraine probably are too.

Avoiding doing anything that might antagonize the bad guys isn't a particularly effective strategy for maintaining a stable and peaceful world. The lesson of Poland in WW2 is that when evil dictators get what they want, they don't calmly stop doing bad things.

Among the countries interested in joining NATO during the 90s was Russia itself, even as it began waging brutal wars against its neighbors, who thereby have earned far more right to be paranoid than Russia has.

If NATO hadn't expanded then Russia would currently be invading Poland and Austria. Why would this be a good thing?

given their immediate prior history, maybe those countries wanted to join so they'd never have to endure the horrors of being under Russian domination yet again?

not even the Russian population wants to be under Russian control