They've historically done a lot of things on their own for JS. So perhaps VS Code + TS language server isn't quite on par with their JS tooling (which works a lot better with TypeScript type definitions, though, so perhaps it's just mostly the same as well).

However, what I personally hated was that there's so many squiggly underlined things ... in red, yellow, green and what other colors, each of which (regardless of color) could be either ignored or an actual error. Granted, that's how easy it is to properly check JS code for whether it does something sensible, but I didn't really find it helpful, especially because issue categorization and accuracy was so random.