Though I use it daily, my biggest criticism of TypeScript is that it's not opinionated enough. From inception it was designed as sugar on top of JavaScript but not a replacement, and therefor they decided not to make decisions outside of the ECMAScript specification.

The advantage to this is developer buy in, the downside is how annoying it is to work with at scale.

In a monorepo, running 10 compilers in watch mode because TS can only consume external source which is compiled to JS. You can't consume TypeScript source directly (which would be nice if you want to use github as a package repository).

But it's fine. I'm happy paying the cost to not use JavaScript directly, but I am disapointed because it could be so much more.