I'd argue that linear games on PS4 still looked a step above open world games with a few exceptions where developement time and budget far exceeded the competition (like RDR 2). But when developement time and effort were relatively similar? IMO, God of War (2018) (linear) was a noticeable step up from Horizon: Zero Dawn (open world).
What the PS4 era really showed is how much time, money, and manpower a developer had was more influential on the final look of a game than anything else and how much more important those things were than in the PS3 era. And that gap is going to grow even larger with the current generation where very very few developers are going to be able to even scratch the surface of what the current gen consoles are graphically capable of just due to the cost in terms of time, money and manpower that is needed to fully realize what the current gen consoles can do.
I'd also argue that Oblivion looked as good as most of the linear games of it's time (2006 console release IIRC).
Regards,
SB