Regarding the outdated design, I did not understand you ...
As for Win Forms support, it seems to me that it has not gone away; you can be sure of this by reading the news about Visual Studio 2017 and .net 4.7.
Personally, my observations:
WPF speaks of tremendous speed in drawing elements on the screen through working on DirectX. My computer is beautiful to everyone - both the CPU and the GPU, but, in fact, the drawing on the screen of Win Forms is much faster (GDI is also not worth it).
The WPF Control DataGrid is extremely raw (at least a couple of years ago). This is the most important control for presenting data in general. It should be very versatile, just like it is in Win Forms, but not in WPF. For data virtualization in a DataGrid (WPF), you can only use virtualization of the data source itself via a DataSource.
In Win Forms with a DataGridView, you can do literally anything you want thanks to the good old event mechanism (CellVlueNeeded and CellValueFormating), and it’s very simple (well, DataSource is also in place).
By the way, can someone tell me, is there a way in the DataGrid to programmatically put focus on line number N without resorting to code in 30 lines using reflection?
In my humble opinion, WPF is good for applications where flying and flying buttons in the form of stars are more important than anything else.
For business applications, everything else is important; people use these applications for a long time, many hours a day. Their functionality is complex and, as a rule, non-standard. Therefore, their interface should be as functional as possible and not delay attention to itself. A person should not get tired of the colorful and cartoon interface.
In favor of WPF, I will only say that the very principle of constructing an interface in it is very interesting in that it is similar to that in Internet pages. This is very interesting, but still damp (until now! When was WPF first introduced!?) ... And yes, I do not like XAML.
-;)