England finished behind Ireland by a difference of six points despite a thrilling 55-35 victory over France at Twickenham on Saturday.
"Four years as runners-up is not acceptable and we are not happy with how that came about," Ritchie said.
"If you go back through history, bearing in mind a lot of things, we should be, as a country, winning more in terms of Grand Slams, Six Nations championships, other things.
"The Irish deserved the win because of what they did over the five matches. We did not do enough over the five matches. There's no point in bleating about it.
"We simply didn't take opportunities, didn't do what we should have done, were not clever enough during parts of the game in order to deserve to win."
England's attentions now turn to the World Cup, where they have been drawn in Pool A alongside twice former champions Australia and Wales.
England begin their World Cup campaign against Fiji on Sept. 18 at Twickenham and Ritchie is confident about the hosts' chances.
"Are we in the frame enough to win it? Yes," Ritchie said.
"I think we've got enough talent now, I think we'll have more talent coming back in when we get to September and I've got to think and believe -- and I know the team and Stuart believe -- that we can win this.
"We should be able to win it. Will we do it? That depends on our application and execution. It's frankly as simple as that."
