i was going to comment. I think even genkernel is compiled, not that i touch the stuff.
I'm not sure if this is possible anymore, but for a while, there was a way to copy over the compiled base system from the disk instead of compiling it all from scratch. Running your first emerge -vaDu world might end up recompiling everything anyway, depending on the age of the ISO, but you didn't have to do any compiling to get a base system deployed.
Yes, there were 3 stages, I think. Stage 3 was with some binaries throw in there. Stage 1 required recompiling the compiler at some point.
There was another way to install Gentoo?