According to what idea of "sensible"?
> encourage a Ukrainian surrender early on and send them some food/whatnot in a care package, then fortify the Polish border.
This would still have resulted in millions of refugees, plus some unknown number of people killed by Russian forces exterminating any local pro-Europe political supporters. Remember Euromaidan. It also snuffs out a democracy, which is not a good precedent to set.
The second motivation is the belief that the invasion, if permitted, will not stop at Ukraine. This is why Finland and Sweden joined NATO after it happened.
> Keeping a conflict worthy of WWII smouldering in the area for more than 4 years now?
Russia can retreat into their internationally recognized borders at any time.
> Can we please be honest about our motivations here?
Can we be honest about the motivations of Russia in capturing and annexing other countries, something forbidden by both the post-WW2 international order and the https://en.wikipedia.org/wiki/Budapest_Memorandum (which also justifies Europe's security provision to Ukraine)?