They had a whole year to bring gameplay and didn't, makes me question the development of the game
This is DC Fandome though, not a game convention. They're showcasing the title as a brand, not as a "game". This isn't an event to speak to gamers, and like KungFucius said, this is still early in the game hype exposure cycle. (Last time was a CG teaser, this is quasi-in-engine, maybe... they didn't even bother with that "The following is realtime footage" blahblah, the suits at DC didn't care enough about gamers to label it properly, they just wanted a highlight to put in the rundown of the show.) Plus, they still have to sell the Gotham Knights game before ramping up Suicide Squad exposure. It's lame that they have a "game" at an event and then don't show it being a game, but this would have been an unusual event for that type of reveal, just like D23 will probably never be a place to see/play a Star Wars or Mickey or Marvel game even though news will probably break for any of those brands at Disney's show some day.
So, the indeterminate state of what was shown was not
quite reason to worry about the status of the project (though you're free to have your doubts, it's not like they
did show anything to assuage fears either, aside from that the story is in place.) Warner Games kind of had to have something of this product at this event, because otherwise it would be a different level of concern, but they didn't have to have anything meaty like gameplay because it's not a big gamer event and The Batman kind of paves over all the other conversation out of Fandome, so SS:KTJL gameplay is still on the marketing roadmap for later and the game is still a long way from selling pre-orders. (I'm sure they're nervous that GK got pushed back a year, now they have to release Knights and Suicide in 2022, assuming Suicide is actually still on track, but they say it is happening...)