But the acronym totally destroys the understandability of the program name and instead is understood as "an unpleasant or stupid person" (https://dictionary.cambridge.org/dictionary/english/gimp).
If you look at similar commercial software you get names like MS Paint, Photoshop or Lightroom.
They should have stuck with "GNU Image", "GNU Photo" or maybe "GNU PhotoEdit".
This.
Nobody's going to forget the name of the browser they use every single day. But if it's some niche tool that I have to look up every time I use it once every few years, that's more difficult.