Concurrent Pascal was an interesting project for its time, heavily dated by now. The greatest victory for concurrency was having architectures with thread-level parallelism instead of the dominant instruction-level parallelism, and one specifically optimized for CSP in the occam language. This was, of course, the transputer. So much for that.
Erlang/OTP leads in the modern era.
But I don't see any relation to our current topic of discussion.
Think all the race conditions, deadlocks, etc that have hit server apps would've happened on Solo, Ada tasking, or SCOOP? Probably fewer to none. So, it's still relevant and Ada/Eiffel are actually building on it. Especially SCOOP R&D community.
Both OpenSMTPD and qmail seem to rely on concurrency through forkexec, which would entail deferring to the kernel's CPU scheduling and job control.
"Event loops seem to have been the norm for C projects for a while."
I'll take you word for it as I've seen that in the few, top-tier ones I scrutinized. There's a similar trail of research dealing with that alternate model. Have a feeling the meme might apply there, too, but won't accuse them until I see for sure. ;)