First, you can simply not use trash frameworks and get better results.

But more importantly, drawing pixels is just one part of a gui and focusing on that without considering the other parts hurts. I've been testing input devices on remote X lately: using programs on my desktop on an old laptop with a touchscreen and a drawing tablet and all kinds of other gadgets. It has different input methods than the client computer. They all just work remotely too, with full capability. Things like copy/paste and drag+drop just working between windows, regardless of where they are running, and integration with local window management is a huge benefit, you can forget these random programs actually run somewhere else. It feels like there's no barrier.