This is definitely an area of recent improvements, and I don't think modern .net (.net core 3.1 - .net 5) is comparable to older school .net here. Whilst GC isn

This is definitely an area of recent improvements, and I don't think modern .net (.net core 3.1 - .net 5) is comparable to older school .net here. Whilst GC isnt quite on JVM level yet (no serious custom GC's afaik), the .net team is clearly paying attention to performance(https://devblogs.microsoft.com/dotnet/performance-improvements-in-net-5/#gc https://devblogs.microsoft.com/dotnet/performance-improvemen...). As you mention, increased ease of use for structs in the form of Span<T> is having quite significant impact in a lot of common .net libraries, aswell as the recent availability of hardware intrinsics for more performance sensitive tasks. I can certainly say F# has had a pretty decent impact in the finance sector in London and likely elsewhere (not sure about HFT however), mostly as a result of this attention to both performance and developer experience.