From my own standpoint, "What are they connecting with?" is a more interesting more of analysis than, "What is flawed with this game?"
That may be true, but I think quite a few readers of this thread came to it actually expecting the game to be good or at least decent after being exposed to Gilbert's earlier work. I myself have played some of WEG's previous games and have been on the fence about buying a few more titles. I don't think anyone here started out hunting for flaws. Given the prevalent mood of disappointment, the question "what went wrong?" is an obvious one to ask, in the sense of "what is different from Gilbert's earlier games?".
Furthermore, even though the question "what are they connecting with?" is of course legitimate, the answer may not necessarily turn out to be particularly interesting or instructive. The Unavowed is adopting a narrative structure that audiences have become accustomed to and conditioned to appreciate by, mostly, Bioware for years. That this has become an established standard in game storytelling doesn't mean that the instruments used to evoke such a positive reception are necessarily particularly sophisticated, rather than simply something that creators have figured out appeals to a large target audience.
Indeed, The Unavowed doesn't seem to be free of such devices that provide audiences plenty to connect with but provide little substance underneath. The entire Star-Trek-V mind-melt vignette, sorry to put it bluntly, reeks of psychological pretentiousness. The subject matter of demonic activity is another example; feels suitably epic to wow a certain target demographic, but do the demons and magic spells really contribute to what might be an interesting tale - that of Codexia's madness and the misdeeds it drives her towards? Granted, the entire "Codexia is Darth Revan" revelation would not have been possible without the instrument of demonic possession, but this climactic moment isn't really exploited either, as has been discussed here, because there isn't any impact on the player character or playing style thereafter, other than a name switch. It might be possible to tell a similar tale, leaving the question of whether the supernatural entities are real or just figments of a psychotic mind unanswered. But then, I'm certain even without having compared sales numbers of the The Shivah and The Unavowed, a game without demons, magic and witchcraft in it is likely to hold much less mass appeal. So, yes, I can see that there's something that audiences are likely to connect with, but it's not something I would be particularly keen on in a game.
Of course there's certainly more than that to the game. The craftsmanship leaves little to be desired for a game of this kind; the artwork is great in some places, and the dialogue writing, for all the holes that the Codex might poke into the plot, seems to be absolutely competent. And there IS some branching (actually, a ton of branching, so much that it is probably to the game's detriment), but unfortunately mostly on a small scale, which is sufficient to evoke the feeling of responsiveness to player decisions. Just like the famous Biowarian dialogues that don't really branch at all, but give you the impression of making an impact as long as you don't replay the game.