>but why do folks say that?

Because it was at some point IIRC,they didn't have a team for it internaly. This was back in the silverlight shutdown, html5/winrt win8 drama. Silverlight actually died, WPF got revived. This is just going on memory, and I wasn't really paying attention to it anyway.

Not sure about WPF, but DLR was pretty much left to die on the vine, which is somewhat sad.

Arguably the DLR accomplished what it set out to do and it is very usable. I've used C#'s dynamic in a number of production project and even a deeper use of DLR constructs (IDynamicObject expression generation) in a few particular sets of circumstances. You can kind of see how Microsoft felt the DLR was "finished" because they solved a lot of the hard problems and made them seem simple and easy.

IronPython and IronRuby are still useful for doing .NET things in a REPL or scripting, though Roslyn's support for C# (and VB) REPL/scripting and F# have lessened the amount of time I spend with IronPython.

(I did recently hear IronPython rebooted and is trying to build out a full CPython 3.5+ compatible version, which was exciting to hear.)

Happy to hear about IronPython trying to get up to speed, I'm using it a lot and it's pretty awesome.

I haven't had the chance to play with Roslyn yet, though. Seems promising.

Nice to hear that IronPython is still seeing some love... I was sad to see (whatever the DLR JavaScript runtime was called) go away when IronRuby and IronPython were picked up.

The UWP XAML stack should be considered the successor to WPF (and for old die hards, Silverlight for that matter as well).