I think the reaction is because there really wasn't a positive atmosphere, on most sites the reveal was slated, the trailer was mocked and there was a lot of criticism and calls for change at PD.
This is just bad damage control, but it's what we should expect from a developer that has only shown disinterest at best to its customers and community.
The problem here is, most of those critics had no foundation at all, the reviews made by some sites were clearly exaggerated (graphics wise), and comments from youtube just show the lack of knowledge from people who see those videos.
Overall the negativity was exaggerated and people made up their mind about the game based on a livestream on youtube of that first build shown on Thursday. After that, just foolish comments about of people claiming thay won't buy the game because it doesn't look "good". That just shows how this industry has evolved.
Graphics are clearly much better compared to GT6, and this was proven by side-by-side comparisons (with GT6).
Sounds are also better, not perfect, but better. Just look for that Corvette video, or the Bugatti one, and everyone will see that there is an improvement and no "vacuum cleaner" sounds.
Physics, as far as we know they have been improved (from the feedback we got from GTP members who attended the event). People expecting this to be a true sim, are not realistic with their expectations since this game is for a large audience, from the more hardcore players, who even enter in competitions to the casual players (which represent the largest part of the community) and for all ages. This is supposed to be something like a Battlefield, not a full-on war simulator, but has some components of that, making it something in the middle of an Arcade and a Sim.