NATO in the post-Soviet era has mainly three purposes:
- To maintain US dominance over Europe
- To keep Russian influence OUT of Europe
- To control Germany and prevent it from becoming a competitive imperialist power again
If Russia were brought into NATO, Europe would eventually gravitate towards it over time instead of the US. So yes, you answered your own question.
Maybe the Sino-Soviet split. It seems like it was destined to happen after Stalin died because of how shitty Khrushchev was, but still, that was an extremely harmful event for the future of humanity. Hopefully we can recover from that mistake.