Don't want to start a flame war, but there's nothing factual correct about what you just said - except for the open source activity around .NET (if that's what you meant by 'stagnant')
Source: Worked for a decade on the .NET stack and for the past few years I've been working on a series of large codebases using Java/Golang/Ruby/Python/the_usual_startup_things. Got my taste of both, still miss C# as a language. I would call Java the most 'stagnant'.
It is a little more nuanced that just being compiled as a poorly optimized compiler can generate slow code. That being said, there has been a ton of work on the .NET Runtime to increase speed. There is even more improvements coming out in .NET Core 3 as well
Source: Worked for a decade on the .NET stack and for the past few years I've been working on a series of large codebases using Java/Golang/Ruby/Python/the_usual_startup_things. Got my taste of both, still miss C# as a language. I would call Java the most 'stagnant'.