To make a more natural eyeliner lood I ease up on the lower lid. Only line the outer 1/3 of your lower eye instead of the entire thing. I usually use a eye kohl and smudge it slightly so it looks like my lower eyelashes are darkened as opposed to I'm wearing eyeliner.
Have you tried the Laura Mercier technique of tightlining? It makes your lashline look thicker, instead of being eyeliner, so could be used for a more natural look.
Apply the eyeliner to the outer 1/3 of your top eyelid and the outer 1/3 of your bottom rim. Make it sort of like a "V" shape. I find that it makes me look more awake and gives off the illusion of defined eyes but doesn't really look like you're wearing much.