You're completely discounting the threat Russia is to ITS neighbors as a possible reason for NATO expansion.
Finland is a perfect example. 20% of Finland was seized by the Russians in WW2 with Finland forced to sign a neutrality agreement.
As the leader of Finland would you continue to rely on those agreements after Putin shredded all his agreements with Ukraine to honor its borders or would you quickly join NATO?
If we were neighbours, you would not believe my words that I meant you no harm if I piled up my armaments along the fence line and had it pointed to your house.
However, you want the Russians to believe our assurances that we mean no harm when we are doing that to them.