"I don't want diversity."
Maybe not, but, and you may not realize this bit, you don't want a monoculture. You may only use one browser, and therefore feel that the other browser technologies are irrelevant to you. You are mistaken there, though. There are trade-offs in every situation, and this one is no different. With fewer rendering engines, it may be easier for developers to write pages that render well everywhere due to less testing surface, but it is at the cost of this necessary diversity. If we all use the same rendering engine, then there is more incentive to create exploits for that engine. Once an exploit is formed, it works on every single device running that browser (you know, the ONLY browser).
Reducing the web browsing options to an ever decreasing number of rendering engines is putting all of our eggs in an ever decreasing number of baskets.