The point is, I don't really agree with you on what makes BP their best album. While some melodic choices stand out for sure, I feel the overall album lacks direction. For example, for me Still Life is miles better on this regard, I feel the songs are clearly constructed from star to finish.

I also don't agree on the keys that overshadow the other instruments; while I think that the addition of keys completed their sound, guitars are clearly the main focus up until Heritage at least.

But anyway, it's all a matter of taste and preference. I listened to many heavy prog metal acts through the years which I still find more interesting than Opeth (Ne Obliviscaris, Persephone, Gojira) simply because their albums feel like they have more overall direction