Why?

So if the U.N were to get involved, which I'm not saying they shouldn't have, I just think it should have been long before the genocide actively occurred. Like when Europe started cultivating the conflict between the two races, or when they assigned superiority to one group over the other

I absolutely agree that the U.N should have intervened in the Rwandan genocide. I do also think you underestimate firstly, how wide spread the genocide was and secondly, how fast it happened. You re also ignoring South Africa's role in it. When the genocide happened all attention was directed toward South Africa as it was transitioning from apartheid to a democracy, so it was getting a lot of attention, including that of the U.N. Also as I mentioned before, there were policies actively KEEPING the U.N from interfering in African politics, so had they gotten involved they would have gotten a considerable amount of backlash on a global scale.