I will not say that they are not healthy, just that some features get outdated and some are added — while some are kept for backward compatibility. C# language itself is the same, just some syntactic sugars have been added to support string interpolation, asynchronous programming, performance improvements for value-type or reference-types.
I believe the soul of C# is same, providing a multi-paradigm programming language. That hasn't changed. Ways of doing things has changed a bit, lambdas, async/await, LINQ and other features introduce amazing new ways to write the programs, leaving practices on the compiler. I would recommend keep reading that, because, as a metaphor, older versions of C# teach you how asynchronous programming works, and newer versions of C# help you write readable and debuggable asynchronous code.
Anyways, for the features and updates in C# language please visit this link and check out what has changed,
The history of C# - C# Guide | Microsoft Docs[
^]. I also recommend using the tutorials provided by Microsoft, they are simplest, straight-forward, and updated tutorials; sometimes not a beginner friendly ones too.
C# Tutorials | Microsoft Docs[
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C# Guide | Microsoft Docs[
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