Glad it's happening, excited to see how well it works! It sounds like perceived needs have changed, and maybe the native APIs allow for bit more flexibility now. There was some discussion of switching back and forth between native and non-native menus based on styling, but that got complicated quickly and it wasn't thought to be worthwhile. The native APIs put heavy limitations on what you could do with a native context menu and it was just not compatible with the expectations of people building against the rendering engine at the time.
People expected to be able to change colors and layout with CSS, for example. It has nothing to do with engineering resources, and we always wanted native context menus, but they were not customizable enough to meet the perceived needs of web, XUL, and extension developers at the time. As someone who used to be involved in the decision to not implement native context menus, and did a bunch of work on the non-native ones, I want to try to explain why this took a long time.
