If we want to be frank about the realities Galway and Limerick are small cities on a European level. You would be surprised what European average actually is, Dublin Belfast believe it or not in journey times is exactly in line with European average
Its slow because it take roundabout route, the route isn't straight and has a lot of up and down.
The media is right to highlight the very clear difference in journey times, all the reports said not to open the line. The money would have been much better spent between Athenry and Galway on providing a commuter service, cost less to build, cost less to run and would generate a large number of passengers.