Tell him its writern in C++ .... He will switch again ;)
Now, building them in C++ feels like carving a tree with a power drill. Better, but still not the right tool
And GTK makes C feel like C++, the bad parts I mean, without the good ones.
I think Android does it in a good way, browsers also made it easier to create nice interfaces, not sure how it works in IOS though.
GTK feels drawn out to me in comparison.
Some libraries manage to iron out the difficulties of the language. QT and WxWidgets are examples of that.
GTK (on C) and Windows MFC are examples of how libraries can make it harder on the user.