The thing is, most of that flexibility or any of the things that could be considered quirks/flaws of the language have been around for a long time and probably

The thing is, most of that flexibility or any of the things that could be considered quirks/flaws of the language have been around for a long time and probably will be due to browser compatibility issues. It isn't great, but it is what it is. I enjoy TS and for web applications I wouldn't want to do without it, but it for sure isn't the "end all" since it still needs to work with those issues. Ultimately though in the case of some of the examples, a type system in a language with optional parameters doesn't excuse you from having to use your brain. Especially if you're the kind of developer who thinks testing your code is just unnecessary.