We should consider the fact neither Afghanistan nor Vietnam were considered as existential threats to the Russian Federation or the USA..
Ukraine is considered an existential threat to Russia, and they will not accept any outcome other than removing that threat permanently.
This maps is almost two years old:
By one recent account, the Russian military is
15% larger today than it was in May of 2022; hopefully we agree Ukraine's military is not larger today than when this map was published.
It strikes me as completely irrational to imagine Ukraine will drive the Russians from the territory they currently occupy.
Kherson: How is Russia imposing its rule in occupied Ukraine?