Seriously, how hard is it to just say, "yes"?

Pretty hard, because saying yes - or no - is inconsistent with Trump's admittedly inchoate foreign policy.

To the extent that there's a Trump Doctrine, it's a belief that most foreign events don't really matter all that much to the U.S. We spend an awful lot of resources trying to influence events all around the globe, but in Trump's eyes they don't really have much of an impact on the U.S., or even our place in the world. Trump doesn't think it's beneficial for the U.S. to be intervening, even through proxies.

From that perspective, there's no yes or no answer to wanting Ukraine to win. Or wanting Russia to win. Or to getting bogged down in the details of what it means for either of them to "win" the conflict at this point (if a permanent stalemate/ceasefire is set with Russia holding about 35% of what it currently holds, who has "won" the fight)? From that perspective, the fighting is far worse for U.S. interests than any end condition that comes out of that fighting.

So Trump can't say yes, because that commits to the U.S. being interested in helping Ukraine win - which Trump doesn't think is worth the effort. Trump can't say no, because that sounds like he wants Russia to win - which Trump probably genuinely doesn't care one way or the other.