One can look into a graph for too long. The Mammoth have a very beautiful, natural, and clear treble. It never sounds dark or muddy, unless the original track was dark and muddy. I have heard many truly dark headphones, and this is not one of them. I almost hate dark headphones unless there is something unique to save them from their overt warm signature.
Also, the Mammoth is the Mammoth. I must say that if you are comparing it with a Solaris, it is doing more than well. I *personally* love its bass tonality, so the biocellulose DD driver is a success in my experience. It is not cheap, but it is not outrageously expensive new-in-box, sealed. "But you can find an used Solaris used almost at that price" is a not so logical conclusion, IMHO.
Vocals are not hazy or distant. Must be my ears, but I am not experiencing these "problems" with the Mammoth. I am sure some tracks with recessed vocals will sound recessed.
This is actually intended for new readers looking for info on the Mammoth, and for Campfire Audio themselves if they get to read this thread at some point. I understand the point of the Mammoth, and am glad I purchased them. I was expecting a bass monster, and yes it's bassy, but it more than shattered my expectations in a positive way.
I think the Mammoth idea should not be thrown away. I prefer this over a Polaris signature (to each their own, of course). They should be two different styles of bassy IEMs at this price point-my humble opinion, for what it's worth. Bassy Vs, bassy Ls, and bassy Ws (Mammoth) have their place, as do neutral reference earphones. Love listening to classical and many non-bassy genres with the Mammoth.
My only caveat is that I have many lower priced and "mid-priced" (i.e. very expensive for my budget) headphones and earphones, and am not able to afford the most expensive audio equipment. But I am also quite firmly convinced you do not need to spend thousands and thousands for a beautiful, immersive audio experience. So for some of us that love great audio but cannot afford all we want, IEMs such as the Holocene and Mammoth make perfect sense, and are a great fit. "Wait 'til you hear this"-I may never hear it due to pricing, and I generally "only" buy new or as-new, open box items.
Be well, and enjoy your music with your favorite gear and 'phones. Like and dislike what you do.
None of the above is aimed at any poster in this thread, so please do not feel offended.