The whole point of establishing a DC Extended Universe is the idea of building up to key figures to include like Aqualad, so it will likely ultimately be in fans’ best interest to wait before demanding his inclusion in the 2018 film.
He deserves the opportunity to really get the spotlight for a while before he has to share it with a popular supporting character.
Though there will certainly be fans out there who are disappointed by this news, it’s also not hard at all to understand the perspective that James Wan is providing.
Yes, it would be great if Aqualad eventually gets to the big screen, and maybe even is part of a live-action Young Justice blockbuster… but let’s not forget that the Aquaman movie is the titular hero’s first ever live-action solo feature.