I'm not familiar with the game or how it should look like but it is quite old and was considered quite intensive at the time which may explain some of the effects present here.
I can give some general observations and tips though:
- The fizzling you prominently see here exists to mask LOD (level of detail) transitions
- LOD appears to be quite low overall; especially textures in the distance
I'd google for LOD issues in AC:Unity.
They probably confused it; 4k 240 and 5k 120 are about the same balpark according to handy dandy chart.