You need to have libgtk installed to run gimp. It would be like running a Qt app (what KDE environment and apps are based on, among other apps like OBS, roblox, google earth, virtual box, etc) without libQt. You couldn’t because the dependencies aren’t installed.

Of course nothing is stopping you from running both, except maybe memory limitations on low ram hardware.

Or you don’t install it as you suggest and use alternative apps.