No, it has special source, because it 1) was literally the first practical photo editing software for home computers 2) has been in continuous development since 1987 and 3) is clearly designed for artists, not programmers. It’s not just how long the development has been, but also how much resources have been poured into it compared to open source and other competitors - and to what end. Gimp may only be just nine years younger, but it’s clearly (just look at its insane user interface) typical of an issue that is very widespread among open source projects: It’s developed by programmers for programmers, with little regard for non-technical users and actual workflows.

Not all open source software suffers from this, but a ton does. It’s frustrating any time I’m trying to get people to e.g. switch to Linux and other open source software; they often run into a wall of poor usability. This is the main thing that prevents mass adoption of the Linux desktop. The fact of the matter is, most developers of open source software are highly technical people who are developing this software for themselves and other highly technical people. This might be fine for you and I, but it won’t win over the better washed masses.