Old school collage. In my opinion, it's the best kind. It's a careful composition of paper elements to create a whole.
Then there's mixed media collage which I also like to practise. While watching a segment on youTube, the artist created something that delighted me, then proceeded to paint over it, add more bits of paper, and paint over that..... I was so disappointed. Gone was that delightful image. Some people I've discussed this with tell me it's to create depth. But you can create depth with one or two layers...it's all in the composition. There's really no need to glue things down and paint over them, then do it all over again umpteen times.
In my opinion.
Simplicity is the removal of the useless and the unnecessary--source unknown