As someone who has worked with a pretty large C# codebase and several smaller ones, I've found it to be one of the least efficient languages to program in. This is maybe not a technical fault of the language, but the way Microsoft encourages developing C# means that once you get past a certain point even simple MRs will have 10-20 files changed. There is sooooooooo much boilerplate caused by .NET that even things like Java Spring Boot just don't have (and even then I'd consider Java to be a pretty bloated language in terms of boilerplate).
That's ignoring the fact that the ecosystem surrounding .NET is a lot more enterprise-y, meaning a good portion of libraries require paid licenses to use.