WPF is quite alive. I had a pretty big audio processing project using WPF a while back, and when I migrated the codebase from .NET Framework to .NET Core 3.1 (and now .NET 5), there were surprisingly noticeable responsiveness improvements. I think they also have some more improvements planned for .NET 6 as well.

Self plug: A while back, I split off my own WPF MVVM framework from that larger project. It's designed for building simple touch-style interfaces, like you would see on a phone/tablet: https://tinyurl.com/upbeatui