[yxhuvud]

Perhaps it is a sign the project is too large and need to be broken up in more manageable parts?

[accurrent]

In my case the problem was: High school kid who is good at coding != software engineer (there are many other nuances to SE, including team management/planning/etc.)

In Cairo's case: Waaaaay too many projects depend on Cairo as a dependency either through GTK+ or otherwise. You will be breaking heaps of backwards compatibility.