And internal websites are a direct competitor to Winforms.

Every year someone telling me Xamarine forms is better now, but every year someone tells me that they tried Xamarine forms the year prior and it still wasn't any good. My one experience with Xamarine forms was watching 3 apps teams (WinPhone, Android, and iOS) all struggle to write an app. Given that it took 3 teams, and it was a large effort, I wasn't impressed, but this was 6 or so years ago. I hope things have improved since then!

Fun fact, for awhile Silverlight was huge in the internal website world, and Microsoft could have easily had another decade of lock-in going on, but then MS killed Silverlight due to internal politics, and even the most loyal MS customers saw the writing on the wall and redirected their internal development efforts elsewhere.

90s Microsoft would never have abandoned a technology stack that had wide spread internal corporate adoption. :/