Better identifying disabled buttons

I find it hard to tell whether a toolbar button that contains a icon, not text, is disabled or not. I added

button:disabled{opacity: 0.5;}

to `gtk-buttons.css` and found the results to be good because the icons are more grayed out:


On the other hand, text buttons become arguably harder to read it (it is a deal for me nonetheless).

Do you agree with my premise in the first paragraph? Is there a way to target only icon buttons for opacity changes?