The alternative would be never refactoring anything and allowing technical debt and complexity to balloon out of control, which would also be a strategic error for a small project without many resources.
The ticking clock you're referring to is real, but it applies to any open source library you're depending on that you aren't contributing anything to, not just GTK. It can't be avoided just by switching to another open source toolkit. If it really bothers you, start contributing and help out!