This statement made me go 'wat' for multiple reasons and I hope you choose to expand upon WTF you're talking about here.
most of the riffs are utterly boring and unoriginal.
boring? sure I can see that, but unoriginal? What?
Watershed is the best post-Still Life Opeth.
Then the same goes to your comments about Agalloch you fucking Opethian fan fag.
Moonsorrow and Agalloch definitely aren't similar bands.
If you heard "Limbs" and think it sounds like Primordial or Moonsorrow, I'm not even going to bother.
In the Shadow of Our Pale Companion is their signature song so that I suppose, but I suggest you listen to The Mantle as a whole.
This thread has gotten really interesting in the last few pages.