system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] Why didn't The Hand ever infiltrate SHIELD or HYDRA?

Considering their whole plan was to find the skeletal remains of a Dragon hidden underneath NYC, one would guess that they'd use SHIELD or HYDRA resources to retrieve what they needed much faster than going through anyone else.
gpt
The Hand are more like thugs than sophisticated espionage agents.  Most of their rank and file spend a lot of time practicing martial arts, packing opioids, and draining blood from vagrants - not skills particularly suited to infiltration.  SHIELD/HYDRA would sniff them out easily.  The top members, the Hand themselves, run things from the shadows and have no need to be part of a large, international organization.

Prior to WW2, HYDRA was mostly  an elite secret society focused on returning Hive to Earth, so there probably wouldn't be any overlap in interests for the Hand.