So What's the deal kishimoto?

[FireBird Marco]

Sage Mode was probably their answer to the Sharingan.

Everyone has sage mode not only Senju, and we don't even know if Senju have sage mode. The only Senju we've seen are Hashirama and Tobirama and neither of them have SM.
Oroshimaru, Jirayia, Kabuto, Tsunade only 1/4 Senju, Naruto not a Senju and Juugo not a Senju.