At first, this song seemed pathetic to me, but after listening to it hundreds of times, I think it’s not that simple of a pathetic song.
It should be noted that I don’t see anything wrong with pathos; on the contrary, I am indeed attracted to this kind of mood, which is why I am obsessed with Shakira's The one, Avril Lavigne's When you're gone, Katy Perry's Thinking of you, and suchlike.  
Shakira’s Illegal, and her music in general, however, doesn’t serve the function of making us cry, for its mourning is so melodramatic that everybody can tell it’s merely acting. Everything about Illegal is so blatantly expressed that no one bothers condemning it as pretentious.
The lyrics about a woman’s heartbroken story couldn’t be clearer, and Shakira’s voice conveyed it quite well. She starts her first lines with a small amount of breathy accentuation that seemingly appears out of nowhere, and when it comes to the next verse, she changed it into a sort of Cranberries-like throaty sound, her signature style, which adds in a sense of escalating anger.

Of course it’s pathetic, but it’s clearly such a feigned patheticness, so it may somewhat brings about the effect similar to that of the ancient Greek dramas in which every emotion is exaggerated so as to satisfy the audience’s insatiable appetite for catharsis. In other words, listening to Shakira’s Illegal, to some people, is seeking pleasure in feigning an acute expression of pain, especially in today’s emotional labour world.
Or maybe that’s just how I see it, after 15 years since its release. This is still one of my favorite songs.