The “realism” of graphics has nothing to do with performance. It has to do with shaders which, contrary to your point can be expected in a greater degree in a game that uses cartoonish graphics BUT I don’t even think that the shaders are the culprit. It really just is that Unreal Engine 5 requires insanely high specs because of all of the myriad different cutting edge technologies it employs, all of which BL4 seems to take advantage of including Lumen, Nanite, and level streaming (idk the name for it)