You mean there are no ideas of interesting things to do with GIMP ?
No I mean that the things that need doing are not exciting to anybody with the time to volunteer to do them. Sure I'd knock some of those off that list if somebody paid me to do it but I'm not interested in spending my free time doing it, there's more fun things to do in the world of software than that. Seems most others share that view too.
Once the volunteers get bored the projects stagnate because the model of users paying devs to add features for them doesn't really work. The case where it does work is when those users are large corporations that can afford to employ and manage contract developers or their own software development department, but of course proprietary software vendors listen to those customers and often act on their requests as a high priority so the customer doesn't have to worry about software development.