There's something about C# that just feels so right for me for backends (as long as you stick to the more modern conventions).
Good tooling, modern language features (C# 15 has the long awaited unions, closed hierarchies), great debugging experience, etc.
If all possible metrics are considered, C# might be the best language ever created.
Yes I think it's a bit underrated. The problem I find is that no one writes C# libraries that actually do anything (e.g. even basic linear algebra is pretty crap compared to python) and that the JIT is a pointless hindrance but the experience of using the stack is pretty good.