User blog comment:Crimson and Darkness/Shin DxD 3 discussion/@comment-77.192.107.58-20190929160022/@comment-10330822-20190929173433

Whose to say he hasn't? The problem with P DxD is not the CxC form, even though that could play into it, its the God power inside of it. After all, when he first obtain DxD G, his body was nearly killed by the Infinity power in it, and it only became managable when Ophis removed most of it. Also, Ajuka already confirmed that its the fact Ophis and Lilith are seperated that makes the DxD G unable to be controlled, and if Ophis and Lilith fused/cooperated, the form would be managable. Likewise, Issei's soul is being affected by the Dragon God aura, making it more and more like a Dragon God's as time goes on and he continues to use P DxD. So, hypothetically, he'll get better with the form the more he uses it, and he'd obtain mastery once Ophis and Lilith are situated.