It's not just Flash.
Superman and Spider-man are quite viable in movies and potential movies. They have been like that for quite a while, and that has not stopped TV producers from constantly creating live-action and animated platforms starring them. Even Batman, who seems to be the only iconic superhero who does not appear in TV live action, actually appears in those (Bruce Wayne was in Gotham, plus all those animated shows starring Batman). That's how Hollywood "conventional wisdom" is: something, anything, is a rule...until it is not.
Not too long ago there was an unwritten rule that claimed that successful superhero movie franchises could NOT interact wirth/exist alongside superhero TV. Well, hello Flash, hello Flashes from the movies and the show meeting in an episode, hello, criticaly acclaimed streaming hit Wandavision and the new Disney Plus MCU shows that will directly link to the movies (Wandavision shenanigans and characters will be a part of Dr. Strange 2 and Captain Marvel 2).
Diana deserves the same amount of constant stream of multimedia showcases that the boys get. That is precisely how the boys become so integrated into/integral to pop culture, and that is why, without even realizing why, people start saying things like "Batman is the best character DC has; that's why he, not Wonder Woman, gets all those showcases" (an actual line uttered by a co-worker). I explained to him that it had nothing to do with which character is "better"; it had to do with how many people in positions of power at these networks and studios prefer Batman (and Spider-man, and Superman), which leads them to constantly create more properties that feature those characters. Then it continues perpetuating the notion that "Batman is the best character DC has." Not too long ago, Wonder Woman was "difficult to translate"...until she was not (because someone FINALLY decided to stop dancing around the subject and produce a film about WW, which everyone and their mother loved).
There is no reason for Diana not to have a prequel live-action show a la Smallville while still having movies about her made.
There is no reason for Diana not to have a solo animated show while movies about her are being made.
In fact, they should do it for her standing as THE superheroine to be even more cemented across all of pop culture.
First establish Diana, then bring in those other girls. Heck, I am dying to see Nubia and Donna in live action (a Donna that doesn't get ridiculously killed by a Batman villain). But Diana should be a priority.