"A Plague Tale: Requiem can be easily described as a GPU-bound title. At 1080p/Ultra, the only GPUs that were able to provide a constant 60fps experience were the RTX 3080, RTX 4090 and AMD RX 6900XT. The NVIDIA RTX2080Ti was also able to provide a smooth experience, though we did notice some drops to 57fps"
This is what I thought and explains why the PS5 is struggling compared to Series X. Make no mistake about it this is a true next generation game (current gen really ).
Jesus Christ, anything to console war, huh?
It's obvious that the optimizations on console-side were focused on Series systems. Remember, Microsoft redesigned the XDK into the GDK which features the exact same API toolset between Xbox platforms and PC due to DX12 Ultimate support.
Plague Tale: Requiem might be an UE5 game but it's also chiefly designed with DX12U, which makes sense because Flight Simulator (also from Asobo) targeted the same (which aided in the eventual Series X and Series S ports). That would mean, considering Asobo's size and what platforms they were already focusing on for the past couple of years, that their pipeline for software optimization on Xbox Series is likely more developed than their software optimization pipeline for PlayStation 5, which does not use DX12U.
Most likely the PS5 version just has less optimizations and the game itself is designed in a way where having fixed function graphics pipeline advantages (such as higher pixel fillrates and a faster GPU) is not as immediately beneficial. The game is leveraging more compute load, and the team probably focused on optimizing that to Series platforms with the DX12U API tools their pipeline is probably already quite mature.
Keep in mind a lot of earlier multiplats that had terrible Series X performance initially were patched and ended up performing better. There's literally no reason why that won't be the case when PS5 initially has the poorer showing in a multiplat. Considering the Series S version is apparently more stable than PS5 and runs closer to Series X, that should clue you in the lack of optimization in its current iteration specifically on PlayStation 5.
EDIT: Apparently this isn't an Unreal Engine game after all? OK then, never mind that part. Still though, I personally think performance issues at least on PS5 is likely due to Asobo's pipeline focused on GDK and DX12U API since they are designing their games for Xbox & PC platforms simultaneously.