To clarify, are you saying that:
1. There are already good reverse proxy libraries in C#?
2. There are already good reverse proxy libraries in other languages?
3. There are already good reverse proxy applications?
If it's #1, then yeah, it would be nice if the ReadMe explained why YARP is different. To be fair, they're at least consolidating a bunch of efforts within Microsoft:
> We found a bunch of internal teams at Microsoft who were either building a reverse proxy for their service or had been asking about APIs and tech for building one, so we decided to get them all together to work on a common solution, this project.
If it's #2, then what do C# developers do? Having to build your proxy in another language isn't a deal-breaker, but there are advantages to keeping your project/team/company on a single language.
(And Microsoft does contribute to Envoy [1][2].)
If it's #3, that only works up to a point. My old team used Nginx, which was perfect in the beginning. But over time we needed to customize things in ways that were difficult to do within Nginx's architecture (either in Lua or in C), leading to hackier and hackier solutions. Using a proxy library to build exactly what you need can make things much simpler.
[1] https://blog.envoyproxy.io/general-availability-of-envoy-on-...
[2] https://techcrunch.com/2020/08/05/microsoft-launches-open-se...