No, it was not. What's called .NET now used to be .NET Core. And then there's .NET Framework which was commonly known as .NET.
> "cannot be tweaked at all"
Are you serious? Not only does the JDK have multiple GCs for different use cases (Serial, Parallel, G1, ZGC, Shenandoah), they have very refined tuning settings (https://wiki.openjdk.org/spaces/zgc/pages/34668579/Main#Main... / https://docs.oracle.com/en/java/javase/25/gctuning/garbage-f...). What does .NET let you do with the GC? Set the hard limit? Maybe turn on/off concurrent collection? That's not tuning, that's triviality.