A symmetric layout feels stable but reads as "seen it" quickly. Asymmetry deliberately mixes big and small elements, wide and narrow space, so the eye moves from one point to another — a technique long used in magazine editorial design.
You build it with uneven CSS Grid columns (grid-template-columns: 2fr 1fr 1.4fr, say) or by giving elements different grid-row/grid-column spans. The point isn't randomness but intentional imbalance — visual weight (size, color, contrast) still needs to sum to something balanced even while left-right symmetry is broken.
Overdo it and it just looks messy. Applying it locally — one hero section, one editorial block — rather than to a whole page fails less often.