Switch's OS is custom made, it's backbone is directly from Nvidia, all firmware, APIs and driver software was created by them. If the platform were to run Android, it would likely not even match the Wii U when in handheld mode, the CPU resources would be lost, memory bandwidth would be heavily reduced. Android isn't even that great of a OS for phones, it would be a huge hindrance to gaming, and while Vulkan helps with some of these resource problems, my understanding is that the scheduler in Android is just inadequate for dedicated gaming, and is designed with a general computing mindset, where interruptions and back ground resources are pulled away at an OS level.
Nintendo's big miss with the Switch was that they didn't opt to use 16nm and 128bit memory bandwidth, they could have fit twice the cuda cores, matched PS4/XB1's CPU, doubled the memory bandwidth. They could have launched a Switch holiday 2016 that more or less was on par with a XB1, they had a really strong deal with Nvidia to use X1 on 20nm, but ultimately it cost them the ability to get games like FF15 for instance, Call of Duty and Assassin's Creed, as well as Monster Hunter Worlds (if Sony didn't lock that down to not be on Nintendo platforms) and even Resident Evil 7... It would have cost Nintendo more money, probably double the SoC cost of $57 dollars, so on par with what the Wii U SoC cost, but that would have drastically improved the validity of the Switch as a long running platform.
They put out something that will over time, change the landscape of gaming, it's not just a successful platform, it has the potential to make consoles obsolete, but in order to do that, a hybrid has to come along with less compromise than the current Switch, whether that is a more powerful Switch in 1 to 5 years, or a competitor's hybrid, we can't know... Eventually someone will come along with a Switch like device that docks into a more powerful GPU, that bridges the gap between these platforms completely and questions why you would have one form factor without the other.