Many (most?) of these are achievable with neovim and tree-sitter (a plugin that gives you access to the AST), and surely many other editors. I have plugins installed right now that do several of the things that are mocked up here. Many more are done with virtual text and not color, but I don’t see why you couldn’t use highlighting instead.
I agree with the broader point of the article that color is underused, but the state of the art has moved way past what the author’s tools are currently configured to provide.
It's some time since I've worked with (and contributed to) tree-sitter, but it could exclusively detect syntax, not semantic, back then. For example it could not tell variables from types in C, nor already-defined variables from new/mistyped ones.
Have I missed an important development in tree-sitter? Can it now do such things?
I agree with the broader point of the article that color is underused, but the state of the art has moved way past what the author’s tools are currently configured to provide.