In before you get people calling you a Marvel fanboy and DC hater. This is simply how business works and how HT can capitalizes on it. It's cyclical. And while they're slow at it, they are pushing out great Arkham-verse figures that are what the DCEU wishes they could do.
It seems that people forget that Marvel doesn't always get all that many figures per solo film either. Black Panther started with two and got bumped to four over a year later. Suicide Squad actually has MORE figures per film than one if the best selling superhero films of all time. Additionally, that's one figure (if you count the 100% reused Rocket) behind Infinity War, Marvel's biggest film. Ant Man and the Wasp is getting two figures, not even the villain, and that did great in China.
Outside Steve Trevor, who else should have been made for Wonder Woman that would have sold? BvS was exhausted, leaving maybe room for a battle damaged Superman.
Justice League flopped. Most EVERYONE has tried to dissociate from that. I commend Prime1 for committing to the whole team, but their margins are WAY different from HT. HT is producing what will definitely sell and cutting their losses.
Marvel also had two advantages, lots of reusable parts and sheer volume. There's 2+ films each year, so naturally that just leads to more product. The fact that there's reusability makes it easier to make more, new product. Look at what is made be HT for DC, characters with right reusable parts mostly.
In short, if DC would get their **** together, then they would have as much product potential as Marvel. It's not HTs fault, though people want it to be. If you ran a store, would you pay for tons of stock for the next DC movie? Hell no you wouldn't, because expectedly it's not going to do well based on history. I have seen next to no Aquaman merch marketing outside Pops, and we are three months away! And that's a stupidly "toyable" film with all the armor and sea creatures. That says a lot for the whole market of DC film product.