In the cartoon, Wally is portrayed as being the youngest of them and being kind of goofy and silly (and wannabe ladies man) in comparison to the rest of the Justice League. He acted more like comic relief in most situations, and he was supposed to be the kid brother type since he was Barry Allen's sidekick and became the Flash only because Barry died.
I think DC took the goofy side of Wally and added that to Barry when that wasn't originally his character, and Ezra Miller doesn't do a good enough job of making that kind of character lovable in this context like Tom Holland did for Spiderman. I haven't watched much of Ezra's previous work, but if they are known for that kind of character, maybe that's why DC hired them. Though, it ended up doing them more harm than good.