Your assertion that ending this war without squarely defeating Russia is exactly the kind of short sighted diplomacy that got us in this mess in the first place. If the US had upheld its guarantees and Russian aggression had been countered when it invaded Crimea we wouldn’t be here now.
It’s not that anyone doesn’t want to hear it, it’s that it is a dam stupid strategy. If Russia gains anything then it emboldens future adventures. Russia doesn’t need to be defeated (as in invaded or overthrown) but it does need to be pushed out of all Ukrainian territory permanently. Anything short is a victory for Russia and sets the world up for further destabilizing actions in the future. In other words there is far more at stake here than just the next one or two years of European gas prices, inflation or other knock on effect.
As far as underestimating Russia, I think we’ve spent the better part of the last 80 years fearing that we were underestimating Russia. Because, well Hitler did.
Frankly I think this has led us to grossly overestimate Russian capabilities.