I’m not the person you replied to, I don’t use Photoshop, but I used to use GIMP exclusively and I use the Affinity suite now. What I’ve seen pop up in discussions about a major area where GIMP is lacking, going back several years at this point:

Photoshop supports nondestructive editing, and Affinity supports nondestructive RAW editing (and even outside RAW editing, it still supports things like filter layers). Heck, my understanding is Krita has support for nondestructive editing, too.

GIMP, on the other hand, has historically only had destructive editing. It looks like they finally added an initial implementation back in February. That’s great, and once GIMP 3.0 releases and that feature is fully supported, then GIMP will be a viable alternative for workflows that require it.