You have changed the definition of Realpolitik then.
https://www.merriam-webster.com/dictionary/realpolitik
I don't know if the Russian invaders are better trained given the snail's pace charge towards victory they are having against Ukraine. Yes, it does outnumber the Ukrainian army in men and material but perhaps suffers from low moral within the ranks none the less.
Yes, I well remember the NATO strategy in Europe during the 1970s having been in the Canadian Naval Reserve at the time. Defence in depth till we could get enough men and material over to turn the tide, maybe. You neglected to mention that the use of tactical nukes was also in the plans for that eventuality. The RCAF had to retrain from the interceptor role to low level delivery of weapons up to and including tactical nukes using F 105 Starfighters. Meanwhile the RCN concentrated on anti submarine warfare to keep the sea lanes open to Europe while practising nuclear transit routines. Thankfully, none of that came to pass.
No it is not too late for Zelenskyy if other countries are willing to get directly involved and risk an escalation of the current conflict to the nuclear level. You know, practice realpolitik.
Bob