One product rarely does everything skin needs. A toner preps, a serum hydrates in multiple layers, a cream seals it in — each step asks something different of your skin, and each one works better because the one before it did its job.
If you only have a minute, a toner and a moisturiser will carry you. If you have three, add a serum in between. The order matters more than the number of products: always thinnest to thickest, water-based before oil-based.
Why a short routine, done in the right order, outperforms a long one done in the wrong order.