That's definately a part of it, DoD:s looks very clean and shiny, whereas the old DoD looked much more war-torn and gritty, and that certainly does change the atmosphere a lot.
But there's more to it than that, DoD was never hardcore realism, but it did mange to both look and play "real enough" that it didn't really bother even a jaded realism nutter like me, alot like RO really, RO also has some big flaws when it comes to realism, but it does play "real enough", and offer a great atmosphere that makes it engaging, and suspends disbelief, its the atmosphere and the playstyle that makes you play them, and lets you look past the wrong details and such.
DoD:s does not have that x factor, it feels alot like playing UT2004 or Q3A, its that kind of fast paced twitch action, and the maps are just a backdrop to the fighting, and weapons that are carefully balanced against eachother (or attempted balanced atleast), the maps don't have the atmosphere, the guns are not belivable in any way, they feel like the generic guns you would find in an arena shooter like UT and Q3A, just pick one you think looks cool and go score yourself some frags..
It seems to be aimed at a fanbase who played UT and Quake and said to themselves "wow, this is really cool, but it would be even cooler with tommy guns and mp40's!", and not so much people who played the DoD mod.. and its in everything really, the graphical style, the map design, the player movement, the guns, its all geared rather differently than the DoD mod was.
Ohh well, i needen't care really, i never bought it, just played some free weekends, so i'm not at a loss here, but i did hope for something very different back when we heard DoD was going retail, i think most of us did.