What began in series one as a recreation of 1950s National Service by series 4 has degenerated into a mildly sadistic sham with any real "recreation" thrown away in favour of more beasting and the random full frontal (male) nudity.
Which is a shame, because the initial series WERE good, and interesting, and asked questions about how relevant or effective National Service might be.
However - even with the first series - the major, overwhelming, problem is that these questions are never properly asked or discussed. The "soldiers" end their course and... we never hear of them again. No follow up (except for at the end of series three where the follow up was barely weeks, so not worth it).
Did the experience have any long-term effect? Did those who join the "real" army stay the course? Where are they now? Could such an experience provide any solution to problems of youth behaviour? Without this it really is a pointless show, and clearly by series 4 ("Extreme") ITV know it. So we now have the "recruits" following a course that bares no resemblance at all to any real 1950s course all with the "prize" of the "winner" going on a parachute jump.
Less "Who dares wins" than "Who cares who wins"! Series 1 deserved 8 stars - but deduct a star for each successive outing!