A Runway can only handle about 20 landings an hour .
Firstly, not so.
Secondly, so what? Space out those 20 landings and you experience less delay.
RTA hasn't definitively solved the problem, but here are the guys (including me) using it as pilots and ATCers telling you it's making a difference.
Sorry if you first thread on PPRUNE has turned out to be less than accurate.