Stuart Pearce's Young Lions left Denmark on Monday still in a state of shock following Sunday night's last-gasp collapse against Czech Republic, which saw them eliminated from the tournament.
England saved their best performance for last and could count themselves unlucky to concede in the final minute and stoppage-time to lose 2-1 in Viborg.
But they still lacked the kind of imagination only Wilshere seems to possess among his peers and which was sorely missing in the costly draws against Spain and Ukraine.
Wilshere performed a dramatic and controversial U-turn over his participation at this summer's tournament after being convinced he could suffer burnout.
Mancienne, who played as a makeshift midfielder in the Arsenal star's absence before losing his place on Sunday, said: "The type of player he is, he's very creative, so he would have made a big difference.
"We would have gone through if we'd had the likes of Jack and Andy Carroll here."
Wilshere's absence highlighted the dearth of technical ability possessed by English midfielders compared to other countries.
Mancienne, who has just joined Hamburg from Chelsea, initially claimed this was not the case but added, tellingly: "Obviously, they play a different type of football to us, they're really good at keeping the ball.
"Our game was to counter-attack.
"We could have done better in the first two games and probably wouldn't have to be in this situation."
Indeed, despite England's pre-tournament travails, head coach Pearce's tactics and team selection were found wanting in Denmark.
He should have been more adventurous following the Spain result, with the degree of changes required coming too late against the Czechs.
One of those was disposing of Mancienne, who insisted he had not been dropped but "rested".
Fabrice Muamba, recalled in place of Mancienne on Sunday night, defended the overall record of Pearce, who has been assured the two-year contract extension he was poised to sign before leaving for Denmark is still on the table.
"You don't judge the gaffer on just one tournament," said Bolton star Muamba, who like Mancienne, was one of the few survivors from the squad which reached the final two years earlier.
"He took us to two semi-finals and one final. I'm sure the team that comes in, in 2013 will do better."
Muamba added of the tournament: "We never really dealt with it properly.
"You'd expect us to win at least one of the first two games and give ourselves a better chance.
"There are always excuses on top of excuses. We just have to look at ourselves in the mirror, look at what went wrong and rectify it in the future."
Muamba insisted that despite the withdrawal of Wilshere and others, under-21 football still had value, adding: "There are many players who want to be in this position."
And more now will be, with Muamba and Mancienne having both ended their long careers at junior level at the age of 23.
Only James Milner has more caps for the under-21s than Muamba, who finished with 33, while Mancienne is just three behind.
Muamba laid down a challenge to the next generation, saying: "It's time for the other boys to come in and take up the shirt and take us to the final and take the trophy back home."
Mancienne added: "I'm a bit disappointed I didn't even get to play."