Visually I guess, but at least their kits have synergy and are themed based on their character. Sivir's gameplay is garbage when compared to Ahri or Riven.
Her gameplay does not fit that at all. You describe Sivir as a mercenary bandit who just wants to be paid and left alone, when her ultimate is this loud ass war cry that causes her to lead her team screaming headfirst into battle. Her kit is suppose to be on a leader, which is why Kled has a version of her ultimate which isn't boring and it fits, because Kled is a general who does lead his troops into battle screaming bloody murder, while Sivir would just rather avoid the fight all together and just steal their money.
Acupuncture. Xayah stuns people by throwing her needle like feathers into their pressure points.
Magnets. He creates a hextech electromagnetic barrier which repels metal.
Geometry. He shoots his grenades the same way Captain America throws his shield. He just sees the angles that he needs to hit for it to bounce how he wants.
Sivir is a fighter, but the lore paints her as the tactical type who favors stealth and experience over a direct assault, and instead of being a leader it sounded like she basically did what she wanted to by herself, and others just followed her.
A good new passive for her would be a contract that she signs with her support for bonus gold and other bonuses, or maybe it could bring up the importance of the Crossblade, forcing her to only have 1 active projectile, and making her attack speed increase how fast it moves, but making it really strong... or both. Maybe the contract could replace the spell shield and allow her to redirect spells to her support.
A new ultimate could be like an Assassin's Creed type thing where Sivir whistles and marks a big area and enemies in it get crosshairs and after a few seconds a bunch of bandits rain arrows down on the targeted enemies, or if you go with the single projectile, maybe she Ascends and becomes surrounded in ethereal crossblades, allowing her to throw as many crossblades as she wants for several seconds, she can even keep the movement speed and attack speed from her current ult.