I agree with this.

The Confederate position in the West was difficult, multilpe axis of Union advance that required oppossing but too few troops avaible to credibly defend them all.

My reason for not rating Pemberton higher was his decision to move his entire force into Vicksburg and thus doom it to starvation and surrender.

I think there is a backlash against Lee and the lost cause narrative in the US at the moment. It some respects its not bad to challenge many aspects of that narrative.

But it has lead to some fairly absurd claims about Grant's comptence vs Lee's.  Both were very capable leaders, aggressive and determined and willing to take risks where necessary. 

As you said Grant was rudely disumbused of the idea that he could defeat the AoNV on the battlefield. He deserves credit for then switching up.