I had seen Lobster before, but not really looked closely. Seeing it again now, I think I was wrong to dismiss it. Just at the syntactic level with semantics described in the link, it looks like it really might be "Python done right". The link mentions lots of features, but the following bits caught my eye.

The let/var declarations for constants/variables is much better than implicit declaration, which silently hides typos and necessitates ugly global/nonlocal declarations. (Mojo offers this improvement too.)

I don't know for sure, but it seems like it's embraced block arguments comparable to how Ruby or SmallTalk does it. So you can add your own control flow, container visitors, etc. I think of this as another syntax for passing a lambda function as an argument, and I'm curious if Lobster's optimizer flattens it to a basic block when possible.

I think I'll try to learn more about it. I wonder if the name is a nod to Accelerando.