Respectfully: I’ve used both quite a bit, and have used .NET since the first release.
If I need a package to perform a task that I think other people surely must have brushed up against in the past then I know it almost certainly exists in npm. That’s just not true for NuGet, as much as it would be better for the ecosystem if it was. This shows in the contributions to each, and the contributions (in terms of volume) are much higher for npm.
Nuget did not exist until around .NET Framework 4.0 (which was 14 years ago).
I specifically noted the post-.NET Framework experience. It is a continuous problem that community demands from the standard library and/or sdk to ship something it has no business shipping (like the sibling comment complaining about System.Drawing, it is truly an 8th OSI layer issue). And when there's an OSS solution, there is a stark difference in comments between developers who understand that OSS projects are projects of collaborative development (meaning that submitting and issue you care about may involve a degree of contribution) and the ones which demand paid level of support for free.
JavaScript is also just generally massive. Surely you're not going to hold it against Rust that Rust projects are less frequently contributed to? C# and .NET are unique language and platform which do overlap with Java and JVM, and other similar class of tools but do solve problems the latter cannot, or solve the ones that they can but in a frequently better way (for example: trying to reach performance ceiling in Java requires way uglier tricks with worse results rather than writing clean byref/pointer based C# code with structs and struct generics).
If I need a package to perform a task that I think other people surely must have brushed up against in the past then I know it almost certainly exists in npm. That’s just not true for NuGet, as much as it would be better for the ecosystem if it was. This shows in the contributions to each, and the contributions (in terms of volume) are much higher for npm.