I remember about 20 years ago in Dublin Airport, at least part of T1 was designed in such a way that arrivals were mixing with people departing as well. I remember being dumped into one part of T1 where there was just a guy standing there at the exit, and CTA arrivals were just waved through with minimal fuss. We were deposited into the departure lounge at the time, and there was no separation of departing and arriving passengers. I haven't used anything other than the Ryanair pier in recent years, so there's always separation there.