While this thread hasn't seen posts in a while, I believe Sui Generis' first impression depends very, very largely on the player.
You actually don't know anything about the plot or world's history, and neither do most of the world's inhabitants. Some of them may even have false information. The development team has chosen to not disclose plot information even during the crucial crowdfunding stage. The following is from an early Kickstarter update:
We have not given you a story. We have intentionally lured you into thinking of this as a fairly typical fantasy RPG. Guess what? We don't like those either. We are of a skeptical nature and when faced with the usual fantasy claptrap, much like an inquisitive child, our answer is simply "but why?". There is lots of because in our world. We have taken what appears to be generic fantasy and given it a whole new twist. A lot of effort has gone into this and to reveal it would be to throw it all away. We hold it more dear than the funds we are trying to raise. If by not revealing it we fail in securing your support, then so be it.
They have done their best to not reveal many of the plot details even at the large risk of failing to secure funding, so it's pretty clear that you, as a player, will have to work to uncover them, and that it's one of the game's most prominent features - this is further supported by the following quote from the same Kickstarter update:
Yes, our world is under duress, you won't be picking daisies. As for a looming threat, you may have no idea what it is until it's too late.
Since you're so largely in control of your own game experience up to the point where you can miss the entire main plotline if you so decide, the first impression of Sui Generis depends on you, as well. You are given the option to miss the entire point of the game, and the game is fine with that, which is great!
However, one important thing that needs to be done is that it's quickly made clear that it's indeed not a 'fairly typical fantasy RPG', since while there's a lot of impressive and groundbreaking engine development going on, to most people gleaning the videos it will look like exactly that. This is probably what prompted the negative '
Sui Generic' kind of feedback; the misdirection from the videos is so good that even news websites end up missing the underlying intent if they don't read through the updates (gaming news websites posting uninformed articles? gasp!)
For people who picked up the game not knowing exactly what to expect, I hope the game at least alludes fairly quickly to the more complex nature of its events, so that people will realize the sheer potential of what the game has to offer (as demonstrated in Komuflage's post). While the combat is revolutionary, in terms of game introduction it should come second to the plot, as that will be what motivates players to complete the game. This is why I've completed Skyrim, even though the combat was fairly disappointing, and subsequently why I pretty much have not restarted since beating the main quest.
The story would be the player's motivation to keep playing the game the first time, and the game's intricate mechanics would keep the player coming back for more. I think the development team is well aware of everything stated above, I'm just trying to add to the thread.