I'm not sure if Square Enix can objectively 'win' this one regardless of how little or how much info is doshed out up to actual release.
- Final Fantasy has redefined itself in significant ways in virtually every entry starting from 6
- Fanbase thus has a very varied idea of what constitutes an ideal Final Fantasy game
- FFXV is arguably the biggest departure from the 'norm' (whatever norm there is) while still maintaining the tenets of the franchise.
- Every video or information blowout results in negative impressions of people who want the opposite (see: #2)
- Every omission of information results in negative impressions of people who want to see how the game is coming along (see: inverse #2)
I honestly think that Duscae is near ideal balance of what Squeenix could have done - a vertical slice with a good portion of the more important core systems (buddies, core combat, exploration, level-up loop, main quest, a summon, offensive equipment, overall aesthetic incl. visuals & music functionality) while leaving out quite a few auxiliary systems (transportation, gambits, defensive equipment, magic, the other ~95% of the world/quests/arcs/etc and virtually all of the story)
I'd argue that of the two lists I mentioned, the former are core to what Square Enix are looking for feedback on to tweak in meaningful ways for polish in the final game, and the latter, while non-insignificant features, either aren't going to change the core experience of the game, or are things Square Enix aren't looking for feedback on anyway (such as the story and setting). The exception to that would be magic which I think definitely would benefit from some public feedback regardless of how well (or not) it's built.
Many of the other issues, especially pertaining to stuff that's explicitly not in the demo (regions other than Duscae, the 'lack of plot', lack of enemy diversity, cities, 'what happened to our grimdark versus XIII' blah blah blah blah) are going to disappear once Duscae drops and the marketing shifts away from it. That's not that far off, anyway.
Considering the somewhat unique decade-long nature of the game's evolution since its inception, and its position as Square Enix's largest egg-basket and all the stakes inherent to that, I'm expecting quite a bit of info leading up to the actual game, but there's two things to keep in mind - one, a game the size of FFXV is going to have way, WAY more to it than can be shown in even a plethora of media blowouts and is going to have a shit ton of surprises in store even if you follow everything, and two, it's completely on you to adhere to a media blackout if you think too much is being revealed if you want to go in fresh. No one has a gun to your head forcing you to spoil yourself silly.