It is still not clear to me what happened. One issue is that there was no big company behind asio and some companies were looking for a more general framework.

Still for what I have seen, sender/receiver only deal with composing async operations, the proposal so far still lack an actual network executor, so it is far from being ready.

This is a shame I think, because while asio might not have been perfect it means that in 2024 C++ still lacks a network library.