I don’t have CC or sliders mods and most of time I don’t mess with more than half of the default sliders, but I believe my sims are different enough.
What I do is first randomize the whole sim or only the face several times until I get some decent starting point and from there I take a caricature approach of selecting a few features and exaggerating them. Like: this girl will have pointy ears and a tiny nose, this guy will have a super squared chin and sleepy eyes.
I think hair, clothes and body already add enough differences, but considering what @cwaddell posted, I think I will check some of my sims made through the years to see if I have a somewhat consistent style.