That works for some applications, but applying that to Photoshop would ruin it. There's too many operations that can't be done at any time, and it's usually obv

That works for some applications, but applying that to Photoshop would ruin it. There's too many operations that can't be done at any time, and it's usually obvious why. Unless you're in Indexed Color mode. Maybe it would be better to gray them out but leave a reason available (tooltip or click).