That's not the only reason. :)
Horrible syntax full of inconsistencies, bolted on type system with TypeScript helps but will always be bolted on, quirks everywhere, as if `null` was not bad enough they also have `undefined`, I can go on.
I simply avoid it for anything but small enhancements scripts on otherwise static HTML pages.
Likewise.
> I know [...] C, C++, C#, Python, Go, various flavors of Assembly
That's good. But these are all languages that either lack strong typing and or are themselves rather quirky.
Only C# and Go stand out, IMHO, as languages that are recently designed. Even Python did not have user defined classes in the first versions, and some things thus feel off (__len__, __init__, etc.).
Also C# and Go still have implicit nulls all over the place. Their designs show ignorance for modern language design. Sum-types, explicit null, immutability, sound type systems -- all lacking in all langs you mention.
So what languages do have these IMHO "Game changers"? OCaml/ReScript/ReasonML, Haskell, Elm, Rust, Gleam, F#, Scala, Kotlin, ...
Those languages really showed _me_ something important: how it could be better.
There is another group of languages that also sits on a unique place in the solution space: the LISPs (incl. Racket, Schemes and Clojure). I found it very worth while to learn to program with them as well.
If you do use C#, you may also want to add <WarningsAsErrors>nullable</WarningsAsErrors> to .csproj too.
The entirety of standard library is annotated since long time ago. All new and not so new projects are also null-aware. Pretty much either completely legacy libraries or libraries that explicitly removed Nullable: enable that is set by default for all new project templates do not have those.
As I mentioned previously - it isn't perfect, but the level of "good enough" of NRTs in .NET is such that the nullability is a solved problem.
And there's a reason practically nobody uses the languages you mentioned, and Javascript is so wildly popular. Most people don't really like or need type nagging systems. Sure, if you're trying to launch a rocket or doing something like building medical equipment or something else that requires covering your ass, then yeah, sure, go ahead and type the hell out of it. But for most programming tasks the languages you mentioned are overkill and frankly too obscure to use.
Also: TS popularity shows that not everyone in the JS community agree with you.
For server side web dev you will find that statically typed langs (Java, Kotlin, C#, Go) are a big chunk of the pie. Sure it also comes down to taste, but if you work in a large team, having stronger types can greatly help to keep the codebase in shape. (better IDE refactor tools, clearer for noob, harder to hide/ check in rubbish to git)
If you are afraid by obscurity, have a look at Kotlin!
TS is to the rescue when you have a big JS project, because that's what JS is not good at: big projects and large teams.