He insists the game has to be marketed better in Australia, so more people who play at the grassroots level become rusted-on A-League fans.
While Gallop said no-one could be happy with the A-League's TV numbers and crowds, he believes 10 A-League teams are not enough and 12 would be preferable.
"Expansion can often have pitfalls and be a very costly venture in Australian sport ... we need to think carefully about that," Gallop told SEN.
He expects progress in the next few months as the game works through a complex set of issues linked to how the A-League operates, raising capital for new teams and the rewards for current owners.
But Gallop was blunt about the A-League this season.
"No-one could be happy with the pure output, in terms of numbers around attendances and ratings," he said.
"Of course, those never tell the full story, the quality of the football has been high, Sydney FC have just played beautiful football and look almost unstoppable.
"But it's another reminder of the competition in the Australian market."
The FFA chief executive said this A-League season had struggled to generate interest in the wake of the Socceroos' 2018 FIFA World Cup qualifying process late last year, then the rugby league World Cup, the Ashes, the BBL and the Australian Open.
"Football needs to actually think about how it's marketed, both at club level and our level as we go into the next season in October," Gallop said.
"The sport has a lot of reason to be optimistic, confident about the future.
"The challenge is to turn those grass roots participants into fans of the A-League.
"It's still a relatively young competition, it doesn't have the generational support of the AFL and NRL."
Gallop was similarly frank about poor A-League TV ratings.
"That's probably been frustrating for us, our clubs and no doubt for Ten and no doubt for Fox Sports as well," he said.