I don't really think so. Not everyone has that defining or really visible flaw. It depends on a story, really, you can take LotR for example. Of 9 main characters, only 2 have real flaws: Boromir is easily manipulated, and Pippin is a bit dim. Two are a bit flawed, like Gimly and Legolas, who are a little bit racist at first. Other five are almost all positive traits: loyal, smart, honorable, able and selfless. Still, all are very good written characters.
Another good example are the MCU (non GotG) main cast, mostly only Tony has real flaws. Banner has his struggles, but both he and Hulk, are mostly positive traits. Cap is a bit bullheaded, but still a paragon.
So, no, your characters don't have to have a real flaw. Real people can't be good at everything, and we all have weaknesses, but even a weakness isn't necessarily a flaw. Like Aang's unwillingness to kill, gave him a bunch of trouble and was perceived as weakness by most (even his previous incarnations), but you can't really call it a character flaw.