It's not just texture size, the amount of information the system is streaming in from the SSD is much higher than what would be possible from the HDD and that's aside from the much lower RAM amount, so the asset variety would suffer a lot. Already just that change would change the look of the game by quite a bit.
The dynamic tessellation in the game for the characters can absolutely be scaled to PS4. It's as simple as:
TesellationFactor = 5 ; for PS4
instead of
TessellationFactor = 10 ; for PS5
It's a switch attribute that reduces the approximation of triangles for curved surfaces. This technique is done all the time with 3rd party consoles and the PC.
SSR - same as any other game.
GI - dynamic light probes. (screenspace approach). Done with many games (i.e. Horizon: Zero Dawn)
HDAO - directional occlusion (screenspace approach). Done with a lot of AAA games (Tomb Raider)
SSD - loading times would suffer on PS4 for sure. The texture compression/decompression would take longer but I don't see it being impossible to run seeing as though you would scale down the texture sizes. They never mention any streaming system, so I'm not sure where that is coming from.
Geometry - they mentioned in the video max of 60k polys for a main character model.
God of War renders more:
The Kratos for God of War (PS4) has 80,000 polygons in total, with 32,000 for the face – 30x what we had for the PS2 models.
“That allowed us to create systems that could deform that geometry and achieve a level of detail for the muscles that we couldn’t do before. On top of that, we used a combination of layers of normal maps for smaller wrinkles and pores that we weren’t able to use in past generations because of the limitation of textures. Kratos (PS4) uses over 140 textures.”
Then you reduce particles, texture variety, the polygon models would also need to be simplified (the PS4 Pro can't handle as many polygon counts as the PS5, I don't know why you say this) and then you end up having a game that looks quite a bit different.
Texture variety stays the same. You don't limit the variety in a port. You limit it's resolution only. I would argue that Infamous:SS has more particle rendering than this game, so I don't see it required to be reduced but that's also possible.
My argument still stands that I believe this game can still be run on a PS4 easily and still look relatively the same. I also
don't think this game is the best looking PS game
ever made. I'm shocked that you guys would throw every single AAA developer that makes exclusives for the PS under the bus for best graphics when there is so much more to the graphics systems with the other games. Capsule AO in UC4/TLOU2 is still a better approximation and looks better than the typical AO that is used in this game, for example.