Lol, fair enough, but the C10k problem these days does have a "just use OS threads" solution. It wasn't free; it took a lot of work across the industry. Computers have gotten both faster both single core and wider number of cores. And kernels have spent the last couple decades really working hard on their schedulers and kernel/user sync primitives to handle those high thread counts.
The native model falls apart under C10M, but to be fair so does traditional epoll/queue/iocp dispatching coroutines model of solving C10K. That's where you start having to keep the network stack and application data plane colocated in the same context as much as possible. That can be done with something like DPDK to keep those both in user space, or Netflix is known for their FreeBSD work making KTLS and sendfile kiss in order to keep the data plane completely in the kernel.
The native model falls apart under C10M, but to be fair so does traditional epoll/queue/iocp dispatching coroutines model of solving C10K. That's where you start having to keep the network stack and application data plane colocated in the same context as much as possible. That can be done with something like DPDK to keep those both in user space, or Netflix is known for their FreeBSD work making KTLS and sendfile kiss in order to keep the data plane completely in the kernel.