That's fair, though there have been several projects that have attempted to be "JS-ish but with some behavior changes with strict type handling sprinkled in for

That's fair, though there have been several projects that have attempted to be "JS-ish but with some behavior changes with strict type handling sprinkled in for optimizations" like the Strong types proposal (cancelled) and Dart (which switched to being a compile to JS language just like Typescript), so I'm currently convinced that the trade-offs aren't obviously worth it and that it's unlikely Typescript will change its priorities in that direction in the near future.