But zoom + motion blur, radial blur, render clouds, lighting effects, mosaic pixellation...
Yeah you could do all of these manually but why? They all have their place in various design, and even the seemingly idiotic filters like plastic wrap can be used well in an abstract art piece.
Generally speaking, filters should at most be accents. If I use one, it's because I am a lazy motherfucker. For professional work, though, I would recommend avoiding all but lighting effects and zoom filters.
Lens flare in and of itself is a horrible, horrible effect that should be outlawed. If you were my teacher I'd be thrilled that you hated it until you made me paint that monstrosity on my own.
I think one of the biggest sins in any design is using a "default" effect. For example you're making a text effect and you drop an outer glow + bevel/emboss. Boom. Everyone fucking know what you did. That shade of yellow on the outside of text makes me cringe whenever I see it.