The UWP XAML stack has been the successor to WPF for a while now.
Windows 7 is the outlier, but this isn't that much of a different argument from the complaints that Windows XP had terrible out-of-the-box support for WPF. The same arguments stopping people from using UWP today seem very deja vu to the arguments against WPF even back when in Windows 7.
UWP XAML isn't even that different from WPF XAML. I've got a feeling for some LOB applications maintaining a UWP and WPF build side-by-side is relatively straightforward (and definitely more straightforward than those of us that for various reasons worked on side-by-side XAML builds for WPF and Silverlight).
The work on wpf was 'finished'. It's not abandoned, but there is no innovation in it anymore. They will keep supporting it, but are looking for a way to do it crossplatform, which isn't an option yet
Essentially Sciter is a crossplatform WPF but using HTML/CSS instead of XAML.
As for me (I am an author of Sciter) the biggest disappointment was the way how styles were implemented in WPF/XAML. Even in 2006 it was clear that style cascading (contextual inheritance) is the way to go. It appears as XAML was not designed from the very beginning to be human readable - just trendy ("XML everywhere" in 2006) replacement of VB's .FRM files. .FRM files were even more human readable/editable ( notation was quite close to YAML).
I would love to be able to use Delphi/Firemonkey for that.