Jack-O is pretty versatile: she has an invuln reversal (2D), a variety of strong normals, command throws (regular and super), and the whole servant system which can be used for both okizeme and zoning.
Ram and I-No aren't very versatile because their toolsets are designed for getting the knockdown and running mixups afterwards, former having midscreen combos that practically always carry to corner for sword setups and latter having the hoverdash that allows quick high-low mixups from any knockdown. Their only reliable reversals are supers, and I-No's isn't even throw invulnerable (unless you do the Burst version of it).
Not being "versatile" doesn't mean the character isn't viable in tournament play, it just means the character is more polarized (eg. good mixup but no defensive options, big damage but bad mobility, etc.) compared to an orthodox character like Ky who has a good set of normals, good DP and projectiles, safe projectile okizeme for mixups, decent movement, decent damage, etc, but isn't particularly great at any single area (which means you need to adapt more to how the opponent plays).