Genertative Fill

How come the generative fill use to be so much more effective, I use to be able to select a subject and ask it to "change shirt color to white t-shirt" and it would do exactly that and it it on the subject, now it replaces the enitre subject, even if I select just the shirt and ask it to change color it generates a totally different image, does anyone know what im doing wrong now? Im doing exactly what I use to do, thanks!