Do you happen to have a reference to GTK implementations of pie menus? The challenge we've run into is that newer versions of GTK "streamline" and remove features, so we have to either discard things or build our own replacement (as one example, we've received many complaints about icons no longer appearing in menus in GIMP 3.0, but that was due to the feature being basically removed in GTK3).

We currently have over 13,000 user-requested issues resolved in our issue tracker, so I don't think we're opposed to user requests. :) I think that's a holdover from an earlier group of developers (there's been a lot of people coming and going in the 30 years that GIMP's been around!). We're also just limited by how fast we can implement certain things due to the number of developers. For instance, I focused on vector layers for GIMP 3.2 - a feature requested by many users! But that meant that I wasn't working on other features requested by other users.