I’m with you in spirit, but please don't bring up gimp in this context.

It’s like mentioning your nephew is pretty good at the piano, when people are discussing if John Williams was copying Holst.

I find Photopea to be completely legitimate, and ripoff is too strong, but you can recognize that it's not just a "fairly feature-comparable alternative". It has most of the functionality at the exact same place, with the exact same shapes, because that will help user if they already know how to work with Photoshop. That makes Photopea a well-executed clone, one that has been reimplemented on another platform from scratch.