GIMP didn’t “just figure out non-destructive editing by 2025”. You’re talking as if it was something that the GIMP development team just decided to randomly add recently, ignoring user demands.

The foundation for that functionality (GEGL) has been in development for ages and was also used for some functionality in 2.6 for a long time. The reason why it took this long is that it’s a pretty fundamental change to how the app works. Also, that meshed with other upcoming changes at the time. Also, small development team.