I'm not saying..., but... idiom
informal （一种礼貌或幽默地表达观点的方式）
used as a polite or humorous way of making a comment or criticism
I'm not saying it was your fault. I just think you could have checked. 我不是说这是你的错，我只是说你应该检查一下。
I'm not saying it's perfect, but it's pretty close. 我不是说这是完美的，但也差不多了。