Eoin Morgan believes a lack of experience cost England as South Africa clinched the one-day international series 3-2 with a five-wicket victory at Newlands.
South Africa captain AB de Villiers hit an unbeaten century as the hosts successfully chased down the 237-run target with relative ease to complete a sensational series comeback.
The Proteas are now one of only two teams ever to have recovered from 2-0 down to win a five -match series, Bangladesh achieving the feat against Pakistan in 2005.
Despite admitting his side had been outplayed, Morgan is confident England's emerging stars will learn from the experience.
Morgan told Sky Sports: "I don't think we did enough. We were outplayed here today. We did have chances in previous games to wrap up the series, but we weren't good enough.
"The opportunities would have been executed if we had more experience in the side, but we're growing and learning.
"We pushed them so hard even though we underperformed. We started with the ball exceptionally well, but it just wasn't enough."
Alex Hales was England's top scorer, notching an impressive 112, but the tourists were made to pay for some poor batting as Kagiso Rabada, Imran Tahir and David Wiese took three wickets apiece.
Hales aside, England were underwhelming at the crease, with only Ben Stokes (29), Joe Root (27), Stuart Broad (13) and Moeen Ali (12) making it into double figures.
Hales added: "It was a very close series throughou. We probably let ourselves down with the bat in the last couple of games; we were 40 or 50 short on both occasions.
"We've got a really exciting side, we've come on a lot since the World Cup last year, we've played some exciting cricket against some top opposition and we're still learning as a squad and we've lost to a really tough South Africa side here."
Reece Topley (three for 41) took two wickets in two balls to briefly revive England hopes, but South Africa were guided by the brilliance of De Villiers, who finished on 101 from 97 balls to seal his 24th ODI century.
The foundations were laid by a century stand between De Villiers and Hashim Amla (59), while Wiese (41 not out) also followed up his impressive showing with the ball to finish off the chase with back-to-back boundaries.
De Villiers said: "I've been a little bit off my game for the past month so it's nice to finish like that in the ODI series and lead from the front.
"It's an integral part of being a captain to lead from the front; you can't just chip in with tiny performances. It was a great team performance and I'm really happy to finish like that.
"I didn't think we were far off in the first two ODIs. The belief was still there; we just had to find that bit of confidence and things turned around."