The latter part of Destiny was little more than glorified Kira fanfiction.
Shinn's problem was that they were trying to do Kamille mkII, in their effort to make Destiny a Zeta mkII, to go with Seed being OYW mkII and then got bored and decided to derail the plot to allow for more Jesus Yamato and his holy beam spam.
There's a reason why Seed and Seed Destiny are usually SRW's whipping boys when it comes to integrating the series with a whole bunch of giant robot pilots that run on hot blood.
That said, go check out Astray. Lowe is a much better character than Kira, Shinn, and Athrun put together.