On the matter of foliage - I think that's the main difference people (myself included) are spotting between the 2013 footage and everything after. Specifically those few seconds snippets of Geralt facing the wolves, the fiend and the flying creatures (ekhidans, I think?). In those tiny parts the foliage does seem better to me - it's more dense and has a nicer variety.
That being said, I still don't think "downgrade" is the only explanation. It's certainly the most appealing because that word is very rousing.
I think that part of it is a play on angles - you don't see in the 2013 footage a top-down camera that will let you easily spot how the foliage is separated by patches of nothing, like we often see in the 2014+ material. Looking at the Brazilian 35min footage, there's a moment when the player moves the camera close to the ground, and to me the grass then seems much better than, well, when he moves the camera to a higher point.
The village GIF is often brought up in this topic, but honestly, I'm not seeing a difference in the foliage there and the foliage here:
Part of that GIFs beauty was how alive it was, with so many things happening on screen. I don't see a reason to think that's no longer the case. Just a few seconds before that screenshot I just posted was taken, the leaves were blowing in the wind around Geralt just like in the village GIF, and there was a faint cloud of sand that brushed past Geralt.
Lastly, and I think this has never come up in this topic - I just rewatched the 2013 material, and I don't see the foliage react to Geralt at all. Now it's not completely interactive in all the material released (big bushes, for example, are static), but grass and bigger plants move according to Geralt's movements, something I haven't seen in the beloved debut and VGX trailers.
Now, hypothetically, if there has been a downgrade and the foliage won't look as great as the 2013 material, it's not taking away for nothing. When it comes down to it, if I could choose between static but detailed foliage to less detailed foliage but one that responds to your movements, I'd go with the second. But that's up to personal preference. People might prefer better looking grass, even if it doesn't move, and there's nothing wrong about that. Different strokes.
People who are adamant about there being a downgrade will consider my post as mental gymnastics or excuses. Oh well. Nothing much I can do there. As I said, I think there is a difference, I like the look of the foliage in 2013 more, but I don't think that necessarily means a downgrade. And for the record, I don't think that ultra settings will change this aspect.
See how frustrating it is?
Like I said though, I'll say no more.
Why don't we stop, then? Maybe I've done it too. If so, I regret it, and I apologize (I suspect my post to Scholdarr might have been a bit too feisty, as well as my PM). I don't like it when I let emotions get the better of me in gaming boards and make me write things I wouldn't of had, under a more clear mind. I still believe that discussions can be pleasant even when people are in deep disagreement.