It is a selling point for me. Photopea can be closed tomorrow, and it will disappear from the face of the Earth. GIMP will never disappear, as it can be downloaded and forked, has no DRM like Photoshop, no ads, runs anywhere.
And Photopea does indeed have ads, and "No Ads" is one of the "features" of the premium subscription, as you can check by going to the account page.
I have absolutely no ads on Photopea.
Gimp doesn't have any AI feature, and you're free to not use any of the Photopea AI features, so not sure why it's relevant?
Yes, we indeed don't need Gimp when we have a free Photoshop equivalent.