As someone currently trying to juggle a massive, extremely complex Python project, our code looks very Java-esque just so we can actually understand what's going on. Java/C# absolutely have a place, but the heavy startup mentality here will always lean towards "whatever lets me pump out my crapware and go to market fastest". Startups aren't known for producing well maintainable code (not that you can't make maintainable code with JS/Python, it just gets much harder at higher complexity scales).