Was this the last great album before all the growling stopped and we were subjected to prog that just wasn't very good.

I would argue that this happened on the Ghost Reveries album... but yes I would agree with your sentiments here, I flippin' love Opeth, and I flippin' love Prog Rock, but Opeth trying to do Prog was so... disappointing I guess.

What I originally loved from Opeth was the balance between the loud and soft, between the angular aggression and the sublime beauty. And they lost that uniqueness when they became just another generic prog band.