I have a friend who works at a big company. He only knows .NET. I asked him about other technologies, but he doesn’t seem to care, he’s paid well. Another friend works in the banking field as a developer using Java and jQuery. I told him about React.js and modern frontend tools, but he only knows jQuery
"he doesn’t seem to care, he’s paid well."
There is your answer. Most people want to have a job where if they are paid well and are reasonably safe, they don't care. I am not saying its a good or bad thing. It's just the way it is.
You cannot convince someone to pick up new things because YOU think thats what they should do. I personally think people should always be learning new things but I cannot expect my friend to do it if thats not what they think.
Why would they learn current tech if their current job doesn't require it?
Switching technologies for an existing large project is a huge risky endeavor, so sticking with your tech stack is usually the right move.
It sounds like he just focuses on backend/server development. The language he uses is irrelevant. I know plenty of incredible developers that focus on backend development, and despite working in TypeScript all day, couldn't tell you much about the current frontend tooling ecosystem. They don't care.
Contentious opinion: most 'full stack' developers are bad at least one half of the stack (and very often both).
Based on my experience, .NET has evolved over the years, and .NET folks have kept up with changes. So they are just as used to updating their skills as anyone else, and if a need comes up where they need to learn React or some other "new" thing, they are perfectly capable of doing so.
The reason they don't is that is simply isn't needed in their work.
This is going to be how many corporate developers operate. They don't need to know the leading edge, often because the leading edge will get you burned.
Plus the guy gets paid well. Why should he care about React?
You don't generally want (and really shouldn't) to be on the leading edge in a corporate setting.
it's easier to stand on shoulders of giants than to write C++. anyone with two neurons should always be challenging themselves and there is plenty to do in C++ but they choose these easier languages and frameworks because they probably have family and outside life.
its the other way around: do new tech developers avoid using the language they learned with (eg. java and .NET)?