Neither WPF nor WinUI are using OS controls for most of their GUI. Their GUI is defined by styles and templates in various XAML files. You can make controls look however you like. Microsoft did a great job back then re-implementing UX of WinXP and Win7 on top of WPF, but unfortunately not the newer Windows versions.

Here’s a third-party project with styles and templates implementing GUI similar to Win10: https://github.com/Kinnara/ModernWpf Their approach seems correct, and the screenshots looking nice. I never needed that library BTW, my clients who need good GUI usually provide professionally-made design which is unrelated to Windows controls.

Also, here’s a relevant GitHub issue https://github.com/dotnet/wpf/issues/5793 which currently says “.NET 7.0 milestone”, however the 7.0 is scheduled for November 2022, i.e. in about 1 year, and they may or may not deliver by then.