I am a typescript skeptic :) But my skepticism mostly comes from an aesthetic point of view. Also I try to limit JavaScript wherever possible, making typescript less of a necessity. But definitely, when you have loosely coupled API’s (back & front), I can definitely see how typing can work. Read more about Gary Bernhardt’s experiences with typescript.
On a more general note: There seems to be a general trend towards type systems again, but I think this is a pendulum. While this trend towards typing is happening, I think the next thing for more dynamic languages will be ML/AI assistance resolving the same errors that strong manual typing by programmers solve; partly this is already happening as languages are able to predict the types with enough typing hints present (implicit typing, type inference).
Also, I believe this typing problem is also a bigger issue in JavaScript than in Ruby (I am aware that this post is about replacing a Ruby sever, and also aware of rbs, which is a type system for ruby). Ruby’s objects typically are of a certain class, whereas Javascript often passes around unstructured classless JavaScript objects. Whenever the data structure becomes too complex for a hash typically a new class is born in ruby. Again, things you can do easily with JS as well, but serialization and simply self observed coding patterns seem to somewhat avoid that.