We aren't sitting idly by. We made contact with the UA in 2014 and, along with the Brits, started to improve their training. We've shipped well over a $100B dollars in lethal aid to Ukraine (hmm, need to find a summary). Our NATO allies have pretty much matched that as a whole, plus taking in the many refuges. At the start of the war, NATO wasn't united. Biden didn't want to commit to fighting in Europe without the rest of Europe on board. We also massively underestimated the RA's competence - and hesitated to act because of the that intelligence failure.
So here we are. Yes, if we wanted to make sure Ukraine won, we have the tools to do it. Between the NATO allies, the decision is to not move that aggressively. It seems the consensus is that we have given Ukraine a sufficient number of advanced weapons, plus training for something like 60K troops out of country, that they should be able to conduct a major, successful summer campaign. If the UA can't do so, the calculus may change.
I certainly am distressed over the casualties and destruction this war has wrought on the Ukrainian people and their country. But, geopolitics is a game played standing on a knife's sharp edge. Better this than 'guns blazing' approach of Bush.