Visual GUI development tools, bound to powerful languages like C, probably do not exist in the 'Linux' world. Why? Oh boy, is that a loaded question!

Not to start a flame war but extreme fragmentation of resources is the reason.

It's important to realize 'Linux' is NOT A DESKTOP. 'GNU/Linux' is NOT A DESKTOP. So we're off to a bad start ... before you're even seeing anything like a desktop, you're looking at trying to co-ordinate many opinions from at least three separate entities: the Torvalds kernel meritocracy/dictatorship; the FSF puritanism; and a graphical team like X Org or the Wayland effort.

That's before the myriad desktop environments are factored in. Oh yeah, whoops, it's not even that simple. The 'Linux' community breaks down its visual elements into 'window managers' and other components. But then you've got ...

LXDE Xfce GNOME KDE Unity (thankfully dead from a fragmentation view)

... and likely more that I've forgotten.

Most likely you've come to Raspberry Pi because it's the latest hyped success story to push the free software cause and fair enough, there's a lot of fantastic benefits free software and cheap SBC hardware has given the world. But there's issues as well. Issues that existed well before the Pi happened, yet don't seem to get acknowledged, let alone discussed, in the 'Linux' world where people don't seem to care what is produced by the movement, so long as the effort is going into open software instead the perceived evil of mainstream software such as the Windows world.