[flimsypremise]

I mean, JS is a language, so this would not really qualify. I have to wonder how you expose the state of your C# app to the JS when that needs to happen. Perhaps... with JSON? In which case you are just doing JSON API + distributed state, except in a more complicated way with C# thrown in for good measure. You could simply render your DOM in JS/TS on the backend and save yourself a step. Hell if you are really that opposed to writing JSON APIs, you can just write a Node app that queries the database directly. I don't really recommend doing this since I think exposing data via APIs is good, but whatever floats your boat.

Either way, at some point your app is running JS/TS and CSS, and those two resources require some type of build process to manage beyond a certain degree of complexity. I lived through the hell of having to determine the load order of JS and CSS files by where the script and style tags occurred in the DOM. It was incredibly difficult to do simple things. Now we can do much more complicated things more easily, but language chauvinists object to doing complex things in what they view as "lightweight" languages. The thing is, the "correct" language to use is generally just the one that does the job best, and in this case JS/TS is specifically optimized for writing applications that interface with the DOM.