And barely any big open source is written in .NET, the only one I can recall without googling is Ryujinx

Jellyfin is one of the bigger ones for sure.

Yup, and Bitwarden is another one. Many larger game publishers run their infrastructure exclusively on .NET like Roblox or Ubisoft.

At the end of the day, all the tools written in Go that are listed above are not exactly paragons of performance.

Ryujinx is probably one of the best showcases of the kind of task that is impossible to solve in Go effectively, and yet can be solved very well with .NET. Or you could look at Garnet which is a pure C# Redis implementation which beats vanilla Redis, KeyDB and Dragonfly.

Many large companies including Google, Uber and so on run a ton of Go services :)

This doesn't make Go's FFI not suck. It's one of the worst across all general purpose languages that are in use today.

Quite true, but it shows how much work Microsoft is yet to do in UNIX shops, and bosting about performance improvements on twitter isn't going to change the culture and attitute towards .NET.

Wouldn't it great if even Azure would contribute to CNCF projects using .NET, instead of Go and Rust, as they do currently?