Personally, I don't see any of our recent presidents or candidates as being war criminals outside of the Bush Administration. Even Trump, although he is a wannabe dictator and a Russian-backed traitor intending to harm this country as much as possible, he's not technically a war criminal either? I guess I only associate that term with those who lied to instigate the Iraq War. I don't extend that to Obama, Hillary, Biden, Trump who simply oversaw the war after it had already been started. And to me Biden and the U.S. don't hold any responsibility for Israel's actions. Biden, Harris, and Democrats have all been criticial of Netanyahu even if they have still support Israel generally--because Israel is separate from Netanyahu much like the U.S. was separate from Trump when he was the president here. Hopefully Netanyahu will be replaced by someone more liberal in the election there considering how unpopular he is.
I agree that no politician is a "hero" necessarily, but I don't see most Democrats as being within striking distance morally of even someone like DeSantis, Pence, etc., much less a Trump. My thoughts about Biden though are complicated. I was never really a Biden supporter, to the point I was sort of hoping Biden would flame out in South Carolina back in the 2020 primary so perhaps Buttigieg would get a chance instead. That said, and I know I'm more among the Bernie crowd here, personally I think Biden ended up being a better president than I would have expected. I was really only resigned to being content if he at least ended the Iraq War and fulfilled the infrastructure platform he ran on. For a little while there, the latter didn't seem like it would happen, but it did. I'm also doubtful Democrats would've generally succeeded in the midterms if the nominee hadn't been Biden. Because he's a "safe White guy," the Right hasn't been able manipulate the anti- fill-in-the-blank-identity energy they did with Obama and Hillary which is where all the extreme vitriol of the last decade came from, and Biden being boring allowed Democrats downticket to disassociate themselves from the party leader at the time the way they probably wouldn't have with another candidate that had more charisma and were able to successfully channel people's anger over MAGA antics and Roe being overturned.
Personally, of the candidates out there, my personal favorites are Whitmer and Buttigieg, then Kamala. I definitely see Warnock and Shapiro as having futures, too. Still, I never once believed Biden was going to replaced on the ballot unless he simply chose himself not to run again--and even that would've happened a year or two ago if he was going to, it's not going to happen in the middle of the election. It all seemed more like the stuff out of conservative fever dreams. Even if there had been a big fight in the primaries, my guess is Biden would still have won since he is the standard bearer and a big primary fight would only have lessened any chance he might have in the general. And honestly, Biden being replaced by another Democrat out-of-nowhere would only guarantee a Trump win to me, it would be showing a sign of weakness on the party's part. Kamala is the only one with almost the same level of name recognition as Biden and Trump; I personally think she's underestimated almost as much as Biden has been in 2020 and 2022, but there's no doubt a lot of insiders don't want to take a chance on her. (Which is funny to me, since I think Biden has seemed like he's been fairly genuine in setting her up for 2024 if he gets re-elected, although who knows about her chances even if that all happened.) The truth is Republicans have always played this game of the current Dem president needing to simply move out of the way for somebody else, they did it with both Clinton and Obama, because they know incumbency is a powerful thing.
That's not to say Biden couldn't lose. The underwhelming debate performance and the next month's terrible headlines is definitely going to cause temporary polling dips for him in the short-term. But I expect the election will still turn out whatever way it was going to regardless, the two candidates are too well-known for anyone to be sitting on the fence. I still ultimately think Biden has the edge in his favor, but I wouldn't be shocked at a Trump election either. I mostly try not to worry about it and hope that our institutions would manage to withstand Trump a second time if that happens, it's really all you can do aside from voting. That isn't to downplay the fact that the worst absolutely could happen in the U.S. as much as any other country, the U.S. government isn't uniquely invulnerable, it could happen anywhere and we already know it definitely will be attempted again with Trump there. Hell, everyone knew it would be attempted the *first* time, even though watching it all happen was still surreal.
As for Third Party candidates, the Jill Stein's and all aren't great candidates just because they're mostly unknown and powerless. Even if we weren't a two-party system, I still wouldn't vote for her or RFK. That said, it is nice to dream that we had ranked-choice voting here.