Apparently it's just your fairly standard career mode but based on what I'm seeing and hearing, it's maybe a bit too, plain for what it could have been? Still beats the crap out of Gran Turismo Sport but that's not saying much when that game was entirely focused on just extensive time trials with a lot of multiplayer features, if you only played solo and offline you were pretty much fucked with sport.
It is very strange when you consider the approach of other Sony Studios when their main focus has solely been on the one player narrative experience, like with God of War, Horizon, Ghost etc. But that's more reflective of what the western market wants I guess, they've obviously found that it was far more worth putting more time and effort into focusing on a platform always online style racer as you can squeeze more money out of people that don't want to do the grind and entice them to take up all the microtransactions, and make sure people aren't cheating/breaking the game, especially when it's the direction they're going with the Gran Turismo now, it's a more larger multiplayer driving focused experience, rather then a growing career based single player style game.
If you're looking for that, best off just sticking with GT 1-4.