Maneuver Warfare: Shiryu's Clear Fruit
I would like to point out that there are special kinds of military strategies involving different types of warfare. In this case, I will be discussing Attrition Warfare in contrast with Maneuver Warfare.
Maneuver warfare is a military strategy which emphasizes movement, initiative and surprise to achieve a position of advantage. Maneuver seeks to inflict losses indirectly by envelopment, encirclement and disruption, while minimizing the need to engage in frontal combat. In contrast to attrition warfare where strength tends to be applied against strength, maneuver warfare attempts to apply strength against weakness in order to accomplish the mission.
I would like to suggest that the way Shiryu uses the Clear Fruit is based on these principles of warfare. He calls it a useful ability, and not necessarily a powerful one. This is true if he is considering the Maneuver Warfare concept as part of its use. Stealth is considered to be one of the most dynamic forms of Maneuver Combat. It allows a person to perform covert operations and allows for more opportunities to move, to take initiative, and to surprise an enemy (the core elements of maneuvering).
In other words, it may not be a powerful fruit on its own, but it is powerful in the sense that it provides one of the greatest Maneuver Warfare elements. Stealth.