Don't worry. Userbenchmark is only a syntetic test that helps you.
Simply tells you that between 100 pc with the same configuration as yours would be in the post 33. It does not tell you what deficit you have compared to the average. Your rig is fantastic.
fristly, as says smashjohn, the test is with a 20% background cpu. Normal is about 2%-4%.
Memory is the only thing that must be tuned. Your memory can speed at 3200 and it run at 2133, as the reportcsays. This is because you don't have enabled XMP at BIOS. You can see at userbenchmark memory report that the graphic shows two montains. The first, the users without XMP enables (where your memory drops) and the other with XMP enabled.
About the processor you can see also the graphic with two mountains. Your procesor I7-8700K can be O.C. The users that don't OC drops in first mountain and the users that O.C. drops at second mountain. you can check the windows energy options and choose the performance optcion vs balanced one. And repeat the test at idle.
About the GPU, the mountain is very narrow and the real differences are very little. I think some GPU are with a little OC.
About the SSD some user can have enabled some samsung features (rapit ...) that improve the benchmark but with no effect in real life. Don't worry about it.
Fix the memory XMP and (only if you want and know) put a little OC and enjoy your pc.