I think Trump's position on calling Putin a war criminal at this point is generally correct, although he could and should have pointed out the seriousness of a lot of the accusations. If you make a formal declaration that Putin is a war criminal (even if he is...), it may make a negotiated settlement harder.
The truth is that regardless of whether or not Putin is a war criminal, he's never going to be held accountable for it because nobody is going to invade Russia to hunt him down and take him into custody. That's not going to happen, nor is any form of "reparations" no matter how much they might be warranted. And for the exact same reason -- nobody is going to want to invade Russia to enforce them.
That being said, the rest of what Trump said about that war is a complete deal-breaker for me. Not being willing to say that he sided with Ukraine at all, and making it clear that he was in favor of ending all aid to Ukraine right off the bat, are things for which I could never vote. He's basically given Russia every incentive to keep the war going in the hope that Trump wins in 2024 and forces a ceasefire upon terms very favorable to Russia.
It's honestly enough so that I may reconsider not voting in the Presidential election.