I certainly see where you’re coming from, but I think the designers of C# have done fairly good job evolving the language to balance backwards compatibility, simplicity (in terms of having “only one way” to do things), and the ergonomics expected of modern languages. I think C++ and JS are great comparisons because C++ has at this point added everything and the kitchen sink to it’s language and standard library, whereas C# has gone much more like JS introducing features that evolve the best practices for writing but still feel and read like essentially the same language. For example, primary constructors still look just like regular C#, it’s just a nicer way to define simple POCOs when desired.

As far as important language features, I think it’s easy to pick on discriminated unions because it seems like C#’s users unanimously want that. However, if you read through proposals and discussions, it’s obvious that there’s a lot of nuance and trade offs in deciding how and what form of discriminated unions should exist in C# (and the designers are very active in working through that nuance and trade off - they said they have a working group that meets weekly to discuss it I believe). And to be fair, they have introduced a LOT of other important features (like records and the vastly improved pattern matching) in just the last few years. Without those features, discriminated unions wouldn’t be nearly as appealing, and those features are great for the language even without DUs.

I think one of the things holding back some of the more impactful features we could see in C# is the need to also update the CLR in many cases to handle things like new kinds of types, new kinds of expressions, etc. TypeScript has the benefit of being executed by a dynamic runtime, but C#'s runtime is unfortunately statically typed, meaning it also needs to be updated with the language. It's also used by multiple languages, for what it's worth.

That being said, if they redirected some of their efforts towards improving the CLR as well, I think they could put out all the cool features they've mostly sidelined, like DUs and some form of their extension everything proposal.

The new list initializing syntax is less boilerplate, no?

I think for arrays it's not really a benefit. But for other types it's superior, compared to the current syntax which just calls add on the list object, which is very inefficient compared to building the whole thing at once which is what this new syntax does.

The great thing about languages like C# is that you really don't need to "catch up". It's incredibly stable and what you know about C#8 (Really could get away with C# 6 or earlier) is more than enough to get you through the grand majority of personal and enterprise programming needs for the next 5-10 years.

New language versions are adding features, improving existing ones, and improving on the ergonomics. Not necessarily breaking or changing anything before it.

That's one of the major selling points really, stability and longevity. Without sacrificing performance, features, or innovation.