My main takeaway from your review is, you like D2 and dislike D3. After watching some of the clips I think they might be going overboard with the dark. In some of the dungeons you cannot even see anything, I wonder if light radius will be a thing. In other areas it is just green and gray. Overall, I think they are a lot farther along in development than what some believe. D4 should be new and exciting and stand on its own. I hope they do not try and placate the vocal minority too much. I do not want a rehash of anything.
My specific about Westmarch is that it did not appear to be a bustling center. I know the storyline was meant to give it a dark and gloomy look as it was under siege, but the general layout was my main issue. Many of the areas in D3 were not true to previous games or were too far off from reality in my opinion to.
The best color palette to use would be a mixture of the two games, but it appears they are going to go full bore away from D3 regardless, which wouldn't give the realism look they are going for. And the green and grey you mentioned is exactly what I want them to change, add a bit of color to it.
I agree they are further along in development than they say they are and wouldn't be surprised by a launch mid/late next year. Maybe even earlier. But as for a rehash, they have to take the best parts of each. D3 blew D2 out of the water in animations and movements and with the D2R if you take a side by side, D2R looks hell of a lot better to me, and is actually the reason I stopped even trying the last 2 seasons of D3 because it just looks bad now and the mindless grind turns appeal to me other than for 2 weeks a season.
There is no completion in D3. That is the issue and if D4 goes the same route of never feeling I completed a character it really ends in the same boat.
I have hopes that it'll be a fun game, but it won't be something I can continually test the boundaries of and play in unique ways.
@Glurin hits the point on their approach.
Honestly, not to promote this site, but they really should come and take a look at the SPF. Pick some of the players brains on why they played this. Same as in I would go over to the BG2 sites and read why people are still playing that 20 years in. D2 is about the choices in equipment and how it isn't a one size fits all approach and is completable with tactics and not just raw damage.