Because Sasuke posessed the weapons even though plot nerfed him from using them
Katsuyu cannot guard anyone. That means she's not a shield.
Now if Tsunade could change her physical makeup to that of Katsuyus that would be useful. But still not a shield.
And post the scan of Katsuyu surviving 8th gate.
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Databook say Katsuyu is immune to all physical attacks
NINJUTSU; Katsuyu Daibunretsu (Katsuyu's Grand Division of the Slugs*)
User: Katsuyu
Supplementary; Rank: none
Main text
Capturing her is impossible already! Because she is a boneless mollusk, she has a fantastical ability to transform at will, that of deciding to divide her whole body or to reunite it. All physical attacks are nullified before this technique. No matter how violent the strike, it won't amount to more than a fruitless attempt. The enemy will just exhaust themselves accordingly and eventually fall to the ground.
Caption
-Her mollusk's body, which has no part that can be grasped, brings forth a full-body division!
Picture comment
-She avoids the attacks by dividing her whole body. And she did so with ease, even against Manda, Orochimaru's summoned Great Snake's firm and tight grip.
*"Katsuyu" is just a custom reading for "namekuji", which translates as "slug".