I'm assuming this runs about a jillion times faster than actual Minecraft?
They should re-write minecraft like this; its performance has always been so awful.
They did. These days “Minecraft” officially refers to the new version, while what you are talking about is called “Minecraft: Java Edition”. As of now, both are maintained, though people are afraid that Java Edition is being phased out in favor of the new one. Main reasons for people preferring the Java Edition is modability and availability of an official server software for self-hosting.