Of course Gaza is not Biden's fault, absolutely not. I'm not saying that. And I'm very much a 'leftie' (much more left than the democrats are in the US in fact, I would be more like Bernie).
However he could certainly be a bit less unwavering in his support for Netanyahu who is really committing atrocities. If I could vote in the US I would still vote for him, but with a heavy heart. I'm sure he's not happy with what is happening in Gaza but I would prefer a president who would not be afraid to speak up. And I'm really starting to worry about his mental state as I mentioned.
I have no ideas either, sadly... But it would be so nice if someone fresh would actually get a chance.
What you could do of course is vote for someone else in the primaries. After all, it will still be a democrat, it won't affect the outcome of the presidential election and at least your voice of dissent is counted somewhere. If a lot of people do this, maybe some bells will ring at the DNC.