First, no language is perfect, and building a real system with growing team(s) is always about making purity vs pragmatism tradeoffs with the main goal of keeping the complexity down as the system scale. The truth is that a system is much more than just the languages it is composed of, and regardless of the purity, exactitude, elegance of a language, sloppy work will always lead to a messy result.
In other words, languages should not be used as a substitute for discipline, good patterns, or scalable best practices, but rather as an enabler of such conducts.
TypeScript favored pragmatism over purity, but it is a very well thought-out, robust, and expressive typing layer on top of JavaScript.
Sure, for the sake of language purity, developers can "bytecode your way" to JavaScript Dart, Java with GWT, ReasonML, Elm, but there is a reason why all of those options, how elegant they might be, have limited traction and relatively short lifespan (at least compared to JS), and that is because they add too much friction points (often unexpected ones) for the sake of language purity, which at the end is a never-ending quest anyway.
TypeScript is a structural typing system which has its differences with commonly known nominal typing systems (which often confused with soundness), and while there are some unsoundness is some specific cases, overall, TypeScript is a very robust and expressive typing system on top of the most pervasive language, JavaScript. Not perfect, but very robust nevertheless and a huge step up from traditional JS. TypeScript combined Modern JS (module, let/const, async/await/promise, arrow function with related scoping, deconstruction, ...) does create a very robust environment to scale code and developers.
We used to all our backend in Java for 20 years (personally comes from Oracle) and we now see nodejs / typescript ecosystem and runtime environment has competitive for big app system. For one of our client, we actually just ported the last of our multi-service system from java to TypeScript, and it got 40% less code and it is better typed than Java. Java's high typing friction and Class-For-Everything purist approach makes good code design more of a contortionism exercise than an intellectual one, and while nowadays most agree that this OO-Obsessed approach was the wrong one, it was considered very pure and "robust" at a time.
Anyway, the short version is what makes a big code base scale is not the purity of any given part (e.g., language) but how the whole can minimize present and future friction points. The less friction, the more velocity. Discipline, best practices, tools, environments, and ecosystem are all part of a whole and one needs to make sure to not over optimize one part on the detriment of the others.
In other words, languages should not be used as a substitute for discipline, good patterns, or scalable best practices, but rather as an enabler of such conducts.
TypeScript favored pragmatism over purity, but it is a very well thought-out, robust, and expressive typing layer on top of JavaScript.
Sure, for the sake of language purity, developers can "bytecode your way" to JavaScript Dart, Java with GWT, ReasonML, Elm, but there is a reason why all of those options, how elegant they might be, have limited traction and relatively short lifespan (at least compared to JS), and that is because they add too much friction points (often unexpected ones) for the sake of language purity, which at the end is a never-ending quest anyway.
TypeScript is a structural typing system which has its differences with commonly known nominal typing systems (which often confused with soundness), and while there are some unsoundness is some specific cases, overall, TypeScript is a very robust and expressive typing system on top of the most pervasive language, JavaScript. Not perfect, but very robust nevertheless and a huge step up from traditional JS. TypeScript combined Modern JS (module, let/const, async/await/promise, arrow function with related scoping, deconstruction, ...) does create a very robust environment to scale code and developers.
We used to all our backend in Java for 20 years (personally comes from Oracle) and we now see nodejs / typescript ecosystem and runtime environment has competitive for big app system. For one of our client, we actually just ported the last of our multi-service system from java to TypeScript, and it got 40% less code and it is better typed than Java. Java's high typing friction and Class-For-Everything purist approach makes good code design more of a contortionism exercise than an intellectual one, and while nowadays most agree that this OO-Obsessed approach was the wrong one, it was considered very pure and "robust" at a time.
Anyway, the short version is what makes a big code base scale is not the purity of any given part (e.g., language) but how the whole can minimize present and future friction points. The less friction, the more velocity. Discipline, best practices, tools, environments, and ecosystem are all part of a whole and one needs to make sure to not over optimize one part on the detriment of the others.