Hmm, Dumb and others have tons of off-road screenshots which make you sweat about your statement...
I'm not sure who the "others" are that you're referring to, but dumb basically doesn't do "screenshots". He has a fucking fantastic sense of photography in these games, but he's basically supplying a constant stream of bullshots that look nothing like the game does running in realtime. We've seen some direct comparisons as to what can happen to a Driveclub scene between realtime and photomode.. it really shouldn't be getting utilized the way it is for comparisons. In photomode I'd agree that Driveclub currently remains untouched (and will probably remain that way until the equally photogenic Gran Turismo turns up), but even if the game contains assets of this quality, they are not represented at anything close to that quality when playing the game. This is why so many people pick up Driveclub, and then remark "it looks nothing like all the images I was seeing", because everything appears muddy and undefined by comparison to the photomode shots, and indeed plenty of other games.
So I re-ask my question for the experts who would come by here :
What is preventing DC to go open world ?
I'm definitely not an "expert", but I've seen this pop up a few times, and I'm always surprised that people think making a game open-world would be as simple as "remove the restrictions". There are tons of things I can think of that an open world game would need to consider that a more linear one doesn't.
Firstly, both games utilize streaming, but in Driveclub's case the next place the player will move to is easily predicted, because they can only follow the track forwards, or backwards. This is even in effect in the photomode, where you're prevented from roaming far from the established course. If you had something more akin FH3's drone mode in Driveclub, this would be an easier claim to make. Sonic Generations also streams the level in as the player moves through it, and it's really really good at doing this at some ridiculous speeds... until the player employs some shortcut that causes them to move through the level off the beaten path, at which point the scenery around you disappears as the game scrambles to get what it needs I order to draw everything to the screen again.
Secondly, in both games aggressive LOD will reduce the quality of assets at a distance.. however, in Horizon's case you can usually approach all them and they will be rendered in full detail, including all those that surround it. So whereas you could create an area 3km from the track containing 1000 trees getting LOD'd into sprites in both, in an open world game you'll probably have to deal with those 1000 trees at close range should the player decide to drive there. In Driveclub, this wouldn't be an issue because you've locked the player to the track and so they can't actually get to them ever... let alone get passed them and look back at the track through the forest. Same goes for stuff like placing a huge mountain 5km from course. You just never have to worry about resolving any of it at a higher details, or having it approached from any angle. This obviously still applies to an open world game to some extent, but is basically limited to the outer circumference of the game's world, rather than a short distance from any given course.
Finally, and this one is less directly about open-world and more of a game design element in general, but pretty most areas in FH3 are also occupied by traffic, in addition to the human controlled players. 12 cars at any one time are all that will ever be present in a scene in Driveclub, whereas 12 player cars that can be comprised of any combination 350+ cars contained in the game, but also AI cars which can also be a different set of cars from any of the players.
There's quite a bit that would need to change in order for Driveclub to do what FH3 does, and vice-versa. There's a lot of talk here comparing the talent of each team, and what would happen if Evolution made a Driveclub 2, or if Playground games had 40% more processing power to work with, or if one switched to linear vs the other switching to open-world... and honestly I think there's too many variables to make sort of meaningful prediction in those regards. Even when talking stuff like FH3 being the second Playground games attempt on XB1, there's the fact that they had shipped FH1 in 2012, when Evolution was probably a year deep into Driveclub's development at that point. Driveclub also had an additional year of development added onto it, and the weather update
still arrived months after launch. Had it realised at the PS4 launch like it was slated to, it would have been a game entirely without weather, and a DC2 may have been when were got the weather system it has now. The "what if" scenarios just aren't really worth it.