Yes, there are missing features (it's not even version 1.0 yet!) but I think the number is very small now and the solution is usually to fill in the gaps yourself—which is possible because iced is totally modular
I've made a spreadsheet editor and a slideshow editor with it so "slimmed down photoshop" seems feasible although admittedly you will likely need to get deep into the renderer (possibly write your own renderer traits and there), but I suppose you're comfortable with that given your goal.
If you're not allergic to Discord, come join us. It's a helpful, awesome tight community IMHO
Link for the lazy: https://discord.gg/3xZJ65GAhd
Project link: https://iced.rs