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I think they mean TS lets too much buggy code typecheck, as compared to Scala.

I don't think that's true. TypeScript's type system is very advanced, and has most of the features you need for type-safe development if you use strict mode (which is the default for projects created with `tsc --init`). It has ADTs, null safety, exhaustiveness checking and the LSP tooling is better than any other language I've tried. The biggest feature that's missing from Scala is HKTs, and even those can be faked in TS.

It doesn't have soundness.

This is by design, and rather well explained in the typescript documentation: the type system is based on structural subtyping, which seems like a good tradeoff to me (but of course, as any design choice, not everyone should agree, and it's fine).

Structural subtyping doesn't imply lack of soundness, OCaml object types have structural subtyping too and OCaml is sound.

I'd be hard pressed to say ADTs are first class citizens in Typescript. If anything, seems more like a hack over some interface primitives to me.

I miss having a solid advanced type system like in Haskell when using something like Typescript or Dart. Typescript feels mostly like Microsoft's attempt on converting Javascript to align more with C# to me.

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