What is actually the projected end-game of people who support this war? It's been three years and ukraine has struggled to make any significant progress at retaking its territory. It should be clear by now that they can't return to their 2014 or even 2022 borders unless the countries backing them become directly involved in a potentially apocalyptic war against Russia, and I haven't seen anybody who wants that, not even the countries clutching their pearls over this incident.
The only three possible outcomes at this point are total Russian victory, peace treaty, and WW3. It's not realistic to think Ukraine will ever bring Russia to its knees on its own.
I think what you're missing is that a peace treaty isn't possible without enforcement. Russia won't agree to any enforcement provisions and Ukraine won't agree without enforcement provisions.
Letting Russia take Ukraine puts all of Eastern Europe at risk and may get us closer to WW3 than simply continuing to support Ukraine from afar with the added benefit of burning down Russia's ability to wage war.
If this does ultimately lead to a large conflict it is NOT because Ukraine didn't roll over, it's because of Russia's actions over the last decade.
I think you're right in that there needs to be enforcement provisions, and maybe Trump should be doing a better job of convincing Ukraine that he intends to provide for those. But I don't think it's necessarily a given that the Russians won't agree to any provisions; they'll say that for the sake of bargaining but if they really meant that they wouldn't be coming to the negotiating table. But even if the Russians really aren't ready to agree to security provisions, coming to the negotiating table does not obligate either side to agree to a deal.
I personally would be much more satisfied with my tax dollars going to Ukraine if they had demonstrated that there is no nonviolent solution to this conflict; from the perspective of Americans this is just another case of two countries squabbling over adjoining territories and that's fairly common among countries that don't have a SoFA or defense pact with America (which, regardless of how passionate the Europeans are about Russia pushing into the frontier of western Europe, currently includes Ukraine).
Yeeeeaah, I really can't see that happening. Ukraine has a much smaller economy, a much smaller pool of conscripts, and less foreign assistance. Ukraine gets more free money and supplies from other countries but Russia is actually getting shock troops from North Korea and that's what Ukraine needs more than anything to win a war of attrition against a significantly larger country.
Putin is an asshole, he doesn't care about sanctions and tbh I'm not confident the Russian people do either. Europe, despite their harsh rhetoric, is still addicted to Russian exports, and their hypocrisy is so bad that there are actually Russian pipelines in Ukrainian territory which the Ukrainians are afraid to sabotage because they don't want to piss off the people who are funding their war.
Maybe if Prigozhin didn't get cold feet during his coup attempt it could have ended the way you describe but I don't think that's the sort of thing that anybody can count on happening again.
If the west crank up things already happening - stopping Russia's oil trade and blowing it it's refineries etc - it would probably get so weak economically that it couldn't really continue the war. At that point you could make a deal, or maybe the Russian government would change or decide it has better things to do.
The trouble with just signing a piece of paper is Putin tends to just ignore those.
I suppose that could work assuming the russkies don't respond to a direct attack on their refineries by escalating to nuclear war, but even so nobody's even trying that. Ukraine is too busy fighting for survival with what scarce resources they have, and none of their backers are even talking about joining the war as true allies.
My point is, it seems like everybody at some subconscious level sees this as Ukraine's problem alone, because even their most ardent supporters aren't treating Putin ss the grave international threat they call him rhetorically. Trump's being pragmatic by trying to end the war on terms that can at least preserve what's left of Ukraine as an independent nation.
The only three possible outcomes at this point are total Russian victory, peace treaty, and WW3. It's not realistic to think Ukraine will ever bring Russia to its knees on its own.