I'm not buying your first point. Within a month of OEMs releasing the Kernel sources, you can find builds of AOSP over at XDA, Lineage OS and other forums. And with the project Trebble in P, we have builds within a week. I don't think it is hard or Google is making it hard to compile.
As for your problems installing it on other boards, where are the drivers for them? Your classic desktop installation comes with drivers for almost every laptop/desktop board. Android doesn't because the vendors don't contribute. A snapdragon SoC requires a binary blob from Qualcomm. There is nothing you can do without it. It has nothing to do with AOSP being opensource or Google controlling it (Google controls other aspects, AKA the Play Services).
As for your problems installing it on other boards, where are the drivers for them? Your classic desktop installation comes with drivers for almost every laptop/desktop board. Android doesn't because the vendors don't contribute. A snapdragon SoC requires a binary blob from Qualcomm. There is nothing you can do without it. It has nothing to do with AOSP being opensource or Google controlling it (Google controls other aspects, AKA the Play Services).