(Delta author here.) You can disable syntax highlighting, either by customizing the {plus,minus}-*-style options to not use 'syntax' as the foreground color, or by selecting the diff-highlight or diff-so-fancy emulation modes. That would allow you to still have some of the other features if they are attractive to you, such as side-by-side view, line numbers, restructuring and streamlining of the default diff format output, copyable code (no +/- characters), etc.
