So my sense is that, for utility-type stuff, the library ecosystem in Java feels bigger because its standard library is anemic. That basically forces Java to have a bigger library ecosystem just to achieve the minimum set of tooling you need just to hit the minimum bar for being a usable general-purpose language.

Joda Time, Apache Commons & Guava, Jersey, Hibernate, etc. - heck, even Dropwizard - are all libraries whose .NET equivalents are just different bits of .NET itself. Similar for Java Mission Control, for that matter.

Where .NET pales, IMO, is for stuff like Hadoop that, while astoundingly helpful for some problem domains, isn't so useful for most enterprise development work.