The touring side played excellently to win the second test at Lord's after losing the toss on a difficult wicket to bat on but they were blown away in the last three matches following a series of spectacular batting collapses.
"The last three tests, we were not up to the mark. We never competed," Dhoni said at the presentation ceremony following his team's defeat by an innings and 244 runs in the final test at The Oval.
"Today's batting was a reflection of a loss of confidence. It's disappointing. The youngsters will have learned, not many will have played here. It's important for them.
"Right from the start, our batsmen haven't performed - it was the lower order. Later on in the series, when the lower order didn't perform, we saw there wasn't enough runs on the board."
India were bowled out for 94 inside 30 overs on Sunday, failing to cope with the conditions and an inspired England pace attack.
"It's demanding over here, but the wickets were good, with nice pace and bounce," said Dhoni who was led India to three test series losses to England in a row.
"With overcast conditions, the ball swings. The England bowlers were very consistent."
Dhoni said he had been powerless to change the momentum of the series.
"We couldn't have done anything different," he said. "We gave Rohit Sharma a game, but who else could we have left out If you are playing with five bowlers, it's very difficult.
"There was no point playing a practice game after the third test. We were here early and we had the resources."
Bhuvneshwar Kumar was named India's man of the series for his consistent seam bowling and useful runs at number nine in the order.
"What is important is what you learn from a series and what you do after," he said.
"In a five-match series it's never easy to maintain performance. We have some inexperienced players who will learn. Being a fast bowler, it is always enjoyable bowling in England. I tried to keep my line and length."