Depends on what you mean by ecosystem, it hasn't been trapped on Windows for about a decade now. The variety of third party libraries available is quite good, while the standard library is robust enough that you don't need NPM nonsense like LeftPad and IsEven and IsNumber.
Are there particular things about the ecosystem that you worry about (or have heard about)? Biggest complaint I would have is that it seems like many popular open source libraries in the .NET ecosystem decide to go closed source and commercial once they get popular enough.
Yup, the commercial libraries. That's pretty big. It's nice the standard library has lots of goodies, but I doubt many projects in reality are zero-dependency
(The amount of times I hear "the standard lib is great!" seems more to attempt to defend the plethora of commercial libraries, more than anything)
The community feels rather insular too? The 9-5 dayjob types with employers who don't understand or embrace open source? At my age I can respect that though
And is Postgresql a 2nd-class citizen? If so, your boss will tell you to use SQL Server surely?
I guess it's hard to get a grasp on the state/health of .NET as to me it seems 99.99999% of the code is in private repos companies, as it's not a popular choice for open source projects. Which itself seems like a proxy signal though