Tree-sitter became more widespread and Emacs took notice and included a bunch of -ts-mode as alternatives to -mode into the core. This is good news and a welcome change, but I have some concerns about the approach.
When I first saw the Tree-sitter talk by Max Brunsfeld I was concerned that the language highlighting “fix” they’re talking about is too much.
Regarding elixir-ts-mode in particular, as noted in https://debbugs.gnu.org/67246, its highlighting is currently being reworked.