The build and dependency systems are an abysmal esoteric, poorly documented mix between csproj files, sln files, random scattered json files, etc.

The standard library in my experience sucks and has all sorts of issues, especially around Uris, DateTimes, etc.

And the ecosystem itself has such a low quality bar, ironically _especially_ with anything made by microsoft. For every nuget package that's well-designed, well-documented, and easy-to-use, there's five which have bugs and undocumented exceptions and poorly-designed APIs.