The Rhinos, who agreed to play the match in Australia after the Storm declined to travel to England, threatened to pull off a shock at AAIMI Park when Ryan Hall gave them the lead with a 10th-minute try.
They went on to concede seven unanswered tries as Melbourne showed their class but former Kangaroo international Wally Lewis told television viewers Leeds would probably come seventh or eighth in the NRL and McDermott also believes they could hold their own.
"I'd like to say that, given 10 games like that, by game eight or nine or game 10, I reckon we'd be up to that level," he told the post-match press conference.
"So we'll learn some massive lessons from that. But unfortunately it will be another couple of games before we're in a game as intense as that and in one played at that level."
The Super League champions went into their eighth World Club Challenge without four senior front-row forwards through injury and lost teenage full-back Jack Walker (knee) and loose forward Steve Ward (calf) before half-time.
McDermott says Walker will need surgery to repair a torn cartilage but may miss only two weeks while Ward, who has only recently returned from shoulder surgery, has suffered a torn calf.
"We still could have been better but they were two really important positions to lose," McDermott said. "In the first half, while I never thought we had a grip on game, I never thought lost it completely either. It was a decent contest.
"It was always a challenge to come here and try to throw something at Melbourne which would trouble them. Five drives and a kick wouldn't have, so we had to try something different.
"But, when you use the ball a bit more than you normally do, you run the risk of making errors and those errors killed us, they gassed us out.
"I thought Melbourne's defence was outstanding, it was suffocating, and the more game went on the better they got, they really warmed up to it.
"We came up with challenging plays and tried to get some second phase going but they were just smothering, it was awesome defence."
Leeds captain Kallum Watkins remained proud of his team's efforts and, like his coach, paid tribute to Melbourne's defence. "It was really tough but exciting out there," Watkins said. "We wanted to back ourselves and play a little bit, move them about and give ourselves an opportunity.
"But I think we shot ourselves in the foot, especially in the first half when we gave them too many opportunities and they punished us.
"We knew that if we gave them opportunities to apply pressure they would be clinical and they showed what a formidable side they are.
"For us there is plenty to learn from. I'm immensely proud of the effort - we never gave up. Things didn't come off for us but you've got to give them a lot of credit for their defence.
"The result didn't go our way and we're pretty disappointed with that. (It was) not meant to be, but we'll move on and focus on Widnes next Sunday."
The Rhinos were full of confidence from the start and their enterprise in running a penalty from in front of the posts in the ninth minute paid off when England winger Ryan Hall accepted a cut-out pass from Ward to go over for the game's first try.
The 4-0 lead was fully deserved as Leeds, striving to overcome the challenge of two referees in front of a 16,029 crowd, tested the Storm defence but it quickly became the Brodie Croft show.
The half-back got prop Jesse Bromwich crashing over for an equalising try on 16 minutes, forced his way over himself seven minutes later and provided the final pass which enabled winger Suliasi Vunivalu to produce a devastating finish on the stroke of half-time.
It was a crucial time to score their third try and, with skipper Cameron Smith kicking two conversions and a penalty, an 18-4 lead presented the visitors with an insurmountable task.
There was certainly no way back once giant substitute Nelson Asofa-Solomona barged his way over eight minutes into the second half and, when second rower Felise Kaufusi ran onto a Croft pass to score his side's fifth try, it became a damage limitation exercise for the Rhinos.
Second rower Brett Delaney showed there was still plenty of fight among the visitors when he got back to pull off a tremendous try-saving tackle on pacy winger Josh Addo-Carr but it was only a slight dent to Melbourne's second-half supremacy.
Centre Will Chambers and loose forward Dale Finucane added further tries in the last 10 minutes as Leeds tired and Cameron Munster rounded off the scoring with his only conversion of the match.
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