Agreed.I don't really write a lot of facial expressions. They always seem so trite to me. I'd just keep them to the minimum. If necessary, I'd describe them as something like "she scrunched her nose" or "he bit his lower lip" or "his lips curled into an easy smile," used sparingly. I'd rather let the dialogue and body language ("he shifted his body in the chair") do the work. One of my editors said too many "he smiled" or "she grinned" or "he nodded" are tiresome and trite. And I agreed.
They should be used sparingly, or the story will start to seem like nothing but characters making a lot of faces at each other. This is true whether you use stock gestures like "she smiled" or florid descriptions of those stock gestures like "the corners of her mouth gradually curved upward and a smile spread across her face while her eyes twinkled like midsummer stars in a cloudless sky." (Gag!)
I think some writers may copy to much from movies and television, where closeups of the face (and actors making faces) are used to convey emotion. Whatever you do, don't limit yourself to having your characters pulling faces all the time. Not only can you employ non-facial gestures, you can also use setting and language to convey emotion.