While there are modern iterations of the JSA in the comics, it’s better if a Justice Society movie follows the team’s exploits during World War II.
Think of it being analogous to when the JSA lived on a different Earth during the Silver Age and the New 52.
Since there’s no indication that there was a team of superheroes operating during the 1940s in the DC Extended Universe, a Justice Society movie would be best suited for this new DC films banner so as not to worry about continuity.
Captain America: The First Avenger and Wonder Woman proved how entertaining period piece superhero movies can be, and much of the JSA’s appeal stems from the legacy they left when battling the Axis powers.