Harding, a straight-talking 63-year-old Australian, said far from the sport becoming more competitive with teams challenging the established order, this Rugby World Cup had highlighted that "there's a big gap building again between the two tiers".
He spoke to AFP ahead of Tonga's 45-24 win over Romania, which at least sent the Pacific Islanders back home on the back of a victory after heavy defeats by the top two teams in the world, Ireland and South Africa.
They pushed Scotland hard - "I think we could have had them," said Harding - but given that the Tongans thought they had their strongest ever team, fortified by former All Blacks, it would seem a disappointing campaign.
Harding, though, thinks they "showed in parts we can be an extremely good team."
"My view is that at the 2015 World Cup, the margins were getting tighter," said Harding.
"I think especially the Six Nations teams have worked really hard over the last eight years and become far more professional and better at what they're doing.
"There's a big gap building again between the two tiers.
"I suppose Australia's falling a little bit at the moment," he said, after the Wallabies crashed out in the group phase. "But they'll come back."
Harding, who has also worked in top-level English rugby and for the Australian Rugby Union, said it was not just a lack of playing Tests against tier-one sides in between World Cups, but having the finances.
Harding secured an Ireland-based sponsor prior to the World Cup and he says the Tongan government help out when they can but frequently they have bigger priorities: "They've had a few natural disasters to deal with."
'Quite moving'
Tonga's last Test against a tier-one side prior to the World Cup was against England in 2021. As for resources, they have just one pitch that is up to Test standard.
"You could say one is bitter but is there any point in being that," he said.
"I can say it's frustrating. Because there's a living, breathing dysfunction between what is expected of a high-performance team as far as the players and the staff are concerned, and what we can actually provide.
"We can't meet those levels. Everybody's expecting the players to play at a certain level.
"But we don't have the resources to provide the means and the tools for them to play at that level."
Harding is not just some gun for hire.
He has devoted a large part of the last 13 years to Tonga - he was high performance director from 2013 but stepped down in 2016 because he was "exhausted".
He returned as CEO in 2021.
Once again he has faced a myriad of challenges, most of them out of his control.
"We've had COVID and volcanoes and tsunamis ," he said, with the latter two occurring in 2022 alone.
"And then we had COVID again. So it's been pretty disruptive," he added, with masterful understatement.
Harding's admiration for the Tongans knows no bounds, and his son Reef was brought up and schooled there.
"It's a wonderful island and it's a pretty remarkable country.
"The resilience Tongan people possess is remarkable and their spirit is fantastic."
One thing that distracts them from the rigours of daily life is rugby.
"It's a national sport," he said. "It's like if it was soccer in England.
"Rugby and Tonga, it's in people's souls. They're born as a rugby player."
Harding, though, says the players also earn respect by helping their communities.
"They've done an amazing job," he said. "Pumping resources into the communities, helping their families and helping villages.
"So the rugby players do a lot for the country.
"It's quite moving. I mean that."
For those reasons Harding dreams of what the possibilities could be for Tongan rugby if they could marry their talent to robust financing.
"It's fascinating to think what could happen to the team if we had the resources and the matches regularly with tier-one sides," he said.
"It's like the talent of the players, if we could just," he said, trailing off.
"There's just so much talent."
