I would just like to understand specific threats or issues with using C# as a language. I've used it for 20 years at this point without issue and the latest IEEE language survey shows that it remains one of the top languages[0]; I'm wondering if you have some insight into why .NET and C# are a bad choice for engineering teams that I've somehow overlooked in my 20 years of working with it.

It sounds like your argument is "because Microsoft".

If you are using VS Code, GitHub, or TypeScript -- well, all those are also controlled by Microsoft, aren't they? Microsoft is the biggest investor in OpenAI and in fact offers their own Azure labeled OpenAI -- are you going to give up on OpenAI because it's Microsoft controlled? React is controlled by Facebook. Go is controlled by Google. So what?

Why use C#?

    - It's a very small step from TypeScript to C# if a team needs higher throughput on the backend[1][2]
    - `System.Linq` provides a superset of JS Array methods and is easy to map from one to the other.
    - It's performance is on par or superior to Go[3] and competitive with Rust[4] while being much easier to adopt because of the language similarity to JS and TS.
    - It is an object-functional hybrid language owing to its influence from F#[5]; discriminated unions are on the roadmap and available today with packages like Dunet and OneOf, it has pattern matching like Rust, extension methods provide flexibility in modelling, named tuples in C# 12 converge even more with TS, it supports destructuring record types and classes, it has immutable record types
    - Minimal APIs are very familiar for teams using Express but need more performance.  I'd actually say that it's a bit simpler than Express on Node for common use cases since there's nothing to import when setting up minimal APIs since it's all first-party Microsoft.
    - Platform support for source generators are a revelation; it removes a lot of boilerplate code while actually improving performance over reflection.
    - Many of the things teams love about modern JS actually have influence from C#.  Lambda expressions in JavaScript, `async/await`, and more.  In fact, C# and JS/TS have been converging (see the linked repo).
    - It's relatively easy to write high throughput code in C# with support for both concurrency (Tasks + Channels) and high level abstractions for parallelism (Task Parallel Library) as well as full access to threading.
    - C# allows easy access to underlying low-level primitives; you can program with high level abstractions for productivity but still have access to call `unsafe` code if needed.
    - EF Core is possibly the best ORM on the market right now in terms of performance, ease of use, maturity, and database engine support.
    - A benefit of a language and runtime backed by Microsoft and used in the enterprise is that security issues get addressed by a team of professional engineers; you don't see the same types of security issues that pop up in the Node/NPM ecosystem.
    - This is a big boon particularly because of the broad standard libraries and first-party libraries for many use cases.  Rather than importing unknown dependencies for common use cases, you end up with a baseline of professionally maintained, OSS code.
    - GitHub's State of the Octoverse report in 2020[6] showed that C# had the least Dependabot alerts and has the least transitive dependencies (less prone to security issues via package managers).
    - As a general purpose language, it can be used in many domains from desktop to devices to web to gaming (both Godot and Unity; RyujinX).
    - It's also quite mature and stable while languages like Rust are still ironing out async and Go just released generics.  C# has been there; done that.

My personal opinion is that C# is the language that most teams want but don't know enough about it or have a bad taste from the .NET Framework days. While the runtime is more complex than Node, the language is very similar to TypeScript owing to its lineage from Anders Hejlsberg. C# and .NET in its current form is a great language and platform to build on.

Besides, if a team is already using VS Code, GitHub, and TypeScript, they're already in the Microsoft controlled ecosystem.

    [0] https://spectrum.ieee.org/the-top-programming-languages-2023
    [1] https://github.com/CharlieDigital/playwright-scrape-api
    [2] https://github.com/CharlieDigital/js-ts-csharp
    [3] https://medium.com/servicetitan-engineering/go-vs-c-part-3-compiler-runtime-type-system-modules-and-everything-else-faa423dddb34
    [4] https://www.techempower.com/benchmarks/#section=data-r21&test=composite&hw=cl
    [5] https://itnext.io/getting-functional-with-c-6c74bf279616
    [6] https://arxiv.org/ftp/arxiv/papers/2110/2110.10246.pdf