Chemistry can get complex, but not the pizza recipe. To make a pizza unique, the best you can do is change the toppings. You can't change the dough recipe significantly (whole wheat vs. white flour is about the best you can do) without changing significantly how it rises, cooks and tastes. You can change all the toppings (sauce, cheese, meats, veggies) but basically a pizza is a pizza. The only real creativity comes in changing the toppings.
I've seen several videos showing how most major pop-songs are formulaic to start off with, employing the same 4 basic cords and make music that essentially sounds the same with most of the differences in the vocals.
I'm inclined to agree, to some degree, that we shouldn't go blatantly ripping off other people without at least giving them credit (I fully support CopyFree licensing fwiw), but at the same time if the music industry has made everything so similar anyways, where do we have room to claim any right to how any other song sounds (no matter how similar)?