I agree, which is why I'm not advocating writing or designing your own toolkit. Instead we as a developer community should focus on the "next generation" of toolkits for the modern cross-platform world. Take all that we have learned from GTK, Qt, Flutter and all the web stuff and incorporate it into something new for the next 10-20 years.

Rust is a nice language for that since it is already a "next-generation" language in terms of memory safety and its momentum is still building. Projects like Druid, while far from ready, are a good starting point.