System calls are not the reason the kernel is bypassed. The cost of the system calls is fixable. For example it is possible to batch them together into a single system call at the end of the event loop iteration or even share a ring buffer with the kernel and talk to the kernel the same way high performance apps talks to the nic. But the problem is that the kernel itself doesn't have high performance architecture, subsystems, drivers, io stacks, etc., so you can't get far using it and there is no point investing time into it. And it is this way, because monolithic kernel doesn't push developers into designing architecture and subsystems that talk to each other purely asynchronously with batching, instead crappy shared memory designs are adopted as they feel easier to monolithic developers, while in fact being both harder and slower to everyone.
