Ukraine being allowed to join NATO would give it the potential backing of the others in that conference, and would presumably send a signal to Putin that if he picks on one he picks in then all.
And I wholeheartedly disagree when you say "... so many in the West have bought into Russia having legitimate grievances." That is not a circulating sentiment or narrative. It MAY appear that way because at this moment we have a tyrannical leader in our country being extremely tolerant of Putin, if not defensive of him, BUT I ASSURE YOU that is not a consensus opinion. That is why we're doing everything we can to remove him from office.
From my best understanding, those that voted for Trump did so out of the false impressions and promises given them by him and the multi-pronged fears he successfully established via media channels, day by day, regarding the rising cost of goods and the "invasion of violent immigrants" taking over the country. People in fear lost site of the most important feature of the U.S., which many of us tried to preserve - it's Constitution and democratic processes.
Please note, Trump did not get about 50% of Americans to vote for him. He received about 50% of only those who actually voted. Many of those who DID vote for him now see him much more clearly and have turned against him; red districts are turning blue. And those that did not vote at all for whatever reason(s) now see the need to have done so, albeit late in the game. If a vote was taken tomorrow it would be a different result. The biggest problem is there's no obvious opposition candidate. And the Dems have to now prove they are not handling things in D.C. like it's business as usual - and they have been rallying to the moment. There's just some inertia they needed to combat.