Well, shouldn’t that be up to the original developer? He made a product and let people use it for free. But no-one is forced to use it. And there are other image editors without any ads. Some are proprietary, and some are FOSS, e.g. GIMP.
I don't know. Shouldn't it be up to Microsoft whether my copy of Windows reports back all of my personal data? Shouldn't it be up to Dell whether my computer can only boot Microsoft operating systems?
What does that have to do with software that is financed by ads?
Why don’t you just install GIMP instead of using Photopea?
Exactly. Did you know that leaving the room during a TV commercial break is theft of service - or so argued TV channel companies in court once?
Uhm, okey. But how is that related to Photopea? Are you arguing that copyright laws are void for software that display ads?