Yeah, .NET is an odd choice to praise for backwards compatibility.
.NET 1 -> .NET 2 was iirc a total break due to the integration of generics, amongst other things. Source code had to be rewritten.
.NET Framework -> .NET Core was another total break. Lots of .NET code that worked on Framework didn't run on Core at all and had to be ported to different library or required other changes.
The fact is, the .NET world has made moves that obsoleted lots of prior code several times. Java never has, unless you count the various boulders rolled down the hill at people using JVM internal APIs.
