If you write one with DPDK, it'll be infinitely more complex but you'll have the opportunity to blow away nginx in performance.

If you make one run on an FPGA you it'll be even more complex.

The lesson is that cutting through abstraction like a hot knife through butter is a necessary mindset for performance but also makes things more difficult. Sockets and thread-per-connection were good approaches when networks were very slow relative to CPUs, and they're still often the simplest approach today.