I really dislike claims like this.
It's an open-world game with hundreds (perhaps thousands) of active vehicles and people running around the city, following schedules. I'm sure there's some behind-the-scenes stuff to keep things from bogging down too much, but the more realistic a simulation becomes, the more demanding it is on the CPU. Visually, there's also a lot going on with a relatively faithful recreation of London. It's not photo-realistic, but all the textures, shadows, lighting, reflections, etc. all tax your GPU -- and that's before enabling ray tracing.
What 'unoptimized' part of the game needs to be fixed? Should Ubisoft cut down the number of AI entities to reduce the CPU load? Drop the geometry levels to make it run better as well? It could, but this isn't the type of game that needs 240 or even 144 fps. It's very playable at anything above around 50 fps, with 60 being more than sufficient. Basically, if you think it's "unoptimized" because it can't run at max details and 150 fps or whatever, that's not the intended design. 4K60 is possible on a variety of cards and settings, just not on midrange stuff. With the next generation of consoles, this is basically going to become the new baseline for graphics and CPU requirements is my expectation.