But he says Clive Woodward's team are on the right track towards World Cup 2003.
John was impressed by the contribution of young players like Jonny Wilkinson, Mike Tindall and Ben Cohen in the successful Six Nations campaign last season.
He gives his views on England and a variety of other rugby topics in his new autobiography, Barry John The King, which was launched in Cardiff on Thursday.
He also selects his Fantasy XV, and there is plenty of Welsh inclusions but not an Englishman in sight.
Recalling the 1999 World Cup when England crashed out to quarter-final opponents South Africa in Paris, John says: "Woodward deservedly took real flack afterwards, because to say his team under-performed is an understatement.
"To me, England did not even compete as well as the opposition towards the end of that South Africa game.
"And with the World Cup coming around only once every four years, that represented a real lost opportunity.
"Woodward's men missed the boat after years of preparation for that moment, having played way below their best."
Since then, England have taken the first Six Nations title and drawn a Test series with the Springboks on South African soil.
Superb
"Woodward has learned from the World Cup experience, and bounced back superbly," adds John.
John, now aged 55, says he would not change anything about his golden career.
Nicknamed The King, he won 25 Wales caps and toured twice with the British Lions, including their historic 1971 Test series triumph in New Zealand.
"Certainly, I would love to be earning some of the money these young guys are getting, but equally I wouldn't have swapped the era I played in," says John.
He was joined at the launch by ffellow Rugby greats Gareth Edwards and Gerald Davies, among others.
"Rugby then was a better game. Half the time today, it is like rugby league - all flat defences and not a lot of space to operate in," he says.
John reveals the reasons why he quit Test rugby in 1972 at the tender age of 27, recalling the pressures associated with top-flight sport.
"I couldn't live three lives - that of someone who had to pay a mortgage with a day job, the life of a so-called star and having to be super-fit to play international sport," he says.
"But the biggest thing was the adulation. You couldn't walk down the street without somebody thrusting a piece of paper at you, requesting your autograph."
In the 207-page book, John talks frankly of his special friendship with wayward soccer genius George Best - who wrote the foreword.
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