Its just such a slow grimey album for me. Compare it to their later stuff which is arguably more poppy and whiney, but actually carries some speed and energy with it. Personal opinion.
I mean I'm not going to judge anyone for their opinion, but it's just a fairly unique one. Mastodon rose to prominence as pioneers of blending sludge and progressive metal along with Baroness. When they released Remission and Leviathan there were no other bands out there that sounded like them.
Their new stuff is still solid, but when I listen to Hushed and Grim I feel like it's very derivative of alt metal from the late nineties, though still with Mastodon's great musicianship.
I've just never heard someone say they're a "big mastodon fan" and really only enjoy their latest albums - it's interesting.
I'm a late Scotsman, you could say. I contribute a lot to the genius annotations of their lyrics on their later stuff, so the obsession is there... but their early stuff just doesn't hold for me.
Its a bit like saying you're a Lovecraft fan, but not being a fan of his earlier stuff when his writing was a little bit immature and not fully fleshed out, despite being completely new at the time.