You're underestimating them both severely, mostly Kakuzu in this predicament. I'll go over a list of what Kakuzu could have added to the capture:
(a): Elemental Variants - Sure we don't see many Elements actually causing severe damage now that it's all about massive-field changing power, but I guarantee you that Kakuzu's Ration: Gian played a massive role in wounding the beast seeing as its piercing power is great.
(b): Jiongu (Threads) - People overlook the small feats that Kakuzu's threads have performed: Sewing together Human Body Parts, Traveling deep underground to conceal its presence, holding up a human body, being physically resistant due to flexibility, & being able to reproduce a near infinite amount. Those threads are greatly underestimated, they by themselves could more than-likely partially restrain a Tailed-Beast's limbs.
(c): Doton: Domu. One of the Top 5 Defenses in the NV which is highly underestimated as well. Any Physical Attacks, as well Elemental Natures not being Raiton could, and would be tanked.
There is so much more Kakuzu could have possibly contributed to capturing Tailed-Beast, but that's just the minority.