With Amazon’s ’99’ documentary premiering on Thursday, the Manchester United supporters long enough in the tooth to remember those jubilant treble celebrations could be forgiven for feeling a little nostalgic. From the highs of the Camp Nou 25 years ago to the lows of Crystal Palace today, the Red Devils side of 2024 could hardly be more removed from the iconic, Premier League, FA Cup and Champions League winners of Sir Alex Ferguson. David Beckham, speaking at the premiere, admits that he and the rest of that legendary crop were fortunate enough to have emerged onto the scene at a time in whi…