My grafted moro was a slow to produce as well. It was a grafted tree and in the ground 5 years before it produced fruit. Got ample sun and fertilizer but wouldn't flower much. When it did begin producing is was susceptible to alternates bearing. Not sure my low biuret regimen (sprayed early to mid January) seemed to help a whole lot with quantity, but seemed to lessen extreme alternate bearing tendency. It didn't start producing good crops until it got fairly large, like 8 feet tall by 6 feet wide.
Sadly, its dead now, victim to temps in the low teens to mid 20's for over 60 hours in mid february. Was planted in 2009, first decent crop in 2014, 2015 nothing, a few more in 2016, 2017 a low crop year, but 2018-2020 were pretty good.