All I can say to this is that hashirama had exeptional life force even among the senju, so even though the senju and uzumaki were known for having this large lifeforce I guess it requires a lot of it.I think it was shown in the anime. But if by just combining Water and Earth; you can create wood; then everybody should be able to use it. Even if you take the Life Force argument; why weren't the Senjus and Uzumakis not able to use it ?
The only connection I can imagine with the Shinju that hashirama does have is that Ashura reincarnated into him. since ashura is a grandson of Kayuga and kayuga had the chakra from the shinju fruit already in her (later combined with the tree to become the ten tails) that's a clear connection and can be a reason for his exceptional lifeforce.And that's what is weird. Why does Hashirama have so much life force ? I would say there is a connection to the Shinju here as the Shinju has tremondous amounts of Lifeforce.
I have wonderd if Hagoromo was capable of preforming wood release, and ashura during his lifetime.