That's a lot like writing off feats because you don't think Alertness is interesting.
*You can do more with incarnum than just skill check bonuses*.
So what can you do with it that merits the language of binding the essence of souls to your body? What fantastic, transcendant, awe-inspiring powers do any of these classes have to offer me? What should grab my imagination about it? What is the best, most fantastic, most amazing thing that someone who is capable of sealing the naked being of pure existence onto their own flesh and blood can do with it?
What, in short, makes it worth the time and effort I'd have to invest in mastering the obscure tongue? Growing limbs and adapting the weapons of others is one of the things I'd expect, and the totemist delivers. Flying? SR? Skill bonuses, to-hit bonuses, damage bonueses, movement bonuses? Piffle. There's a million and one things that do that already, and it's just book learning, faith, personality, and austerity in them. When a cleric manipulates a single soul he can bring the dead back from the afterlife after weeks in the dirt. When an Incarnate manipulates many souls sharing epic powers and heroism throughout time and space he....can hit a bit better?
MoI doesn't fail at all in mechanics. The mechanics are solid and interesting. It fails in tying those mechanics to a good concept. On flavor, it falls down, and it falls *hard*.
However, I do agree that it isn't much for big, flashy magic. That's psionics and regular magic. Did we need Yet Another system that was exactly the same? The difference between psionics and regular magic is... power points. Ooh.
I'm manipulating the stuff of souls, here. I should be creating life, wrestling heroic spirits, embodying the great heroes not just to give me a slightly better chance to hit, but to drive home the fact that I can call on great heroes to empower me. I should be overwhelmed by powers beyond my own, and overwhelming those who oppose me. I should be scattering my foes like chaff in the wind with blows of epic legend. I should be defining where life ends and where it begins, giving birth to complete beings out of myself, shaping screaming spirits into my own playthings.
The language and flavor of MoI is big and flashy. Heck, it's bigger and flashier than almost anything else that there could possibly be. But the powers do not stack up. So the flavor -- one of the core pillars of the book -- needs to be entirely overhauled.
Psionics and magic are not dramtically different in mechanics. That's not really my point. The mechanics of MoI are fine. Psionics and magic are dramatically different in flavor.
The Wizard studies dusty tomes in secretive towers and acadamies where knowledge and pure intellectual power break the bonds of reality and redefine the laws of physics. This allows him to throw balls of fire, see accross the world, travel the planes, and mutate his body, and the bodies of others. The wizard exists in definition -- he can prove that you are a toad as he turns you into one.
The Cleric devoutly worships his chosen deity, offering prayers and sacrifice in exchange for deific might. His devotion defines the world around him, and his adherence to that devotion's code enables him to enact his faith on the world. Either he borrows some of the infinite cosmic power of the gods (who never allow much to seep into the hands of mortals), or he uses only the power of his own conviction to redefine the way the world works. He convinces the world that he is right, and the world listens. That is why he is able to heal the sick, smite his foes, and gain and impart personal power. The cleric exists in the superhuman -- he can tap the celestial sphere, and make you more than you can be alone.
The Psion abuses herself with austere rigors, subjecting his body and mind to stresses, drugs, and experiences designed to break her limitations. Her stress and her pain open up vistas beyond imagining, beyond the normal bounds of mortal life, and her mental discipline allows her to use that energy to pierce the world, to re-envision it in the way she sees. The crystals speak of transcendance, of rock that has become more than rock through millennia of honing, stress, and strain. Likewise, she becomes more of a person in the same ways, cutting and refining herself, leaving scars and tatoos, mentally jarring herself out of the everyday to see what lies beyond. This is why they can travel through time, manipulate the mind, see the future, and change their own forms. The psion exists in the breaking point between here and there, you and her -- she can cross the barrier, change the world, and return to herself.
The Incarnate...or the Soulborn...does, what, exactly? Devotes themselves to an ideal like a cleric, kind of...but they either can or can't manipulate Incarnum. And there seems to be no source for this other than others who can do the same thing. It's not a logical extention of self, it's not a personal power in the world. And yet, apparently, one's own health, hardiness, and resilience allows one to manipualte the stuff of souls. The spirits are supposedly all-inclusive: time and space are meaningless to Incarnum. Yet Incarnum basically only powers up the user, letting them do what they could do (or what magic items or other spellcasters could help them do) slightly better than they could do it before. But it's not self-betterment, self-augmentation, or self-adjustment...it's external, manipulating a force, bringing it to bear on you. That force should be immensely powerful -- it is the stuff of all souls, after all. And yet what it does isn't that mighty. Heck, all a wizard does is study books, and he can fly around. All a cleric does is burn some incesnse and learn some prayers, and he can make himself better at hitting. All a psion does is fast and recite some koans, and she can pierce time and space. As an Incarnate, I manipulate the infinity of souls. I should blow these pretenders out of the water, because, hey, THE INFINITY OF ALL SOULS EVER IN TIME AND SPACE vs. your dusty old book! Scissors beats paper, man! But what can I actually do? I can maybe see magical auras, fly around, and, depending on my alignment, do some fancy footwork in the front rank. The infinity of souls at my disposal, and I make pretty helmets and sandals out of them? Seems like a collossal waste....at least the Totemist can grow some limbs and spit some fire and act like a monster.
If the flavor was different, it wouldn't be so bad. It's not hard to make different flavor. Make it mechanical augmentations to the body (golemcraft exists, after all). Make them polymorphic alterations of form (we do have lots of shapechangers in the game). Make it the craft of the greatest of smiths (I think the book could've just leaned more heavily on the Moradin/Dwarf idea and done just fine, too). Make it some unholy necromancy where you dig up body parts and replace your own with them (you are your own Frankenstien). Make it a pact with outsiders where angels rush to your aid or a demon replaces your body (this is probably the direction I would take it, actually). Make it about ghosts, about nature spirits, or about a team of helpful squirrels who run out of your bum, all over your body, and manage to help you with the things you need to do. But don't make it about the stuff of souls made substance and expect to be able to get away with "Now you can run faster!"
And as the leader in the inudstry, it is WotC's bloody JOB to be able to figure this out. They should be providing me with things I can use, not interesting ideas I have to half-cobble together to make some semblance of work. Not things that I could describe better given a few hours to ponder. They obviously do a bang-up job on designing rules. But that doesn't let them off the hook for designing a bad framing device. The framing device is arguably many orders of magnitude MORE important than rules.