> After a significant amount of experience in the .NET ecosystem, I believe the majority of the anti-Microsoft sentiment is well-deserved. At one point, there was a lot of innovation in .NET OSS, but it seems to have ground to a halt within the last few years. It's possible I'm just projecting because of my own experience, but it seems like many of the more influential members of the .NET ecosystem have gone on to do other things.

That's not entirely true. Pretty much the entire ASP.net MVC stack has now been open-source. Entity Framework is also open-source.

I agree, 3rd party OSS ecosystem is much smaller than Java.