Is this a serious question?

This is the exact same ridiculous argument that proprietary software corporations make. It never made any sense, security through obscurity will never work. Linux is open-source used on ~80% of all web servers, in your logic these servers would all be vulnerable. It just doesn’t make any sense. Linux is also used in many embedded devices and Android is based on the Linux kernel. But Android (which is also entirely open source) has one of the best security models out there.