Holmburgers, interesting you say that. I also paint, and have always had similar issues there, although it's not exactly the same.
I am still enjoying photography. The excitement of seeing something you want to make a photo of, picturing the final print etc is still there. It has just become harder for me to move on from a particular idea. Part of the problem is alot of my subject matter is near to where I live. So I make the picture, but each time I drive by that location I can't help thinking things like "hmm, maybe with today's lighting the conditions are better than when I originally made the picture", or "hey now that it's November there are no distracting weeds sticking up through the sidewalk, I should redo the photo now". This is dangerous thinking because it makes you want to fix things all the time.
As for being very critical of the work of great photographers, this I am more comfortable with. I think it is ok. I now prefer to think of myself as a fan of particular images and prints rather than having to say I like x photographer or y photographer, although obviously there are certain photographers who have produced more work that resonates with me.