I've read in multiple places that Leticia was not at all spreading negativity on set. I've read that she has been very pleasant and that some things were taken WAY out of proportion.
I think the issue is how much time is needed for post-production and how much filming still needs to be done. Three months were devoted for filming of the first film (Jan. 21-April 19, 2017). Ten months were spent in post. One might think that more time is needed for BP2 due to underwater Atlantis being a major part of the film. Thus, even if they completely wrapped filming, they'd likely STILL need more time than they have before a November release.
And not one but two superhero movies with Atlantis as a major setpiece are scheduled within a month of each other (BP2 and Aqua2). That's not to mention the water-based behemoth that will be Avatar 2. Within the course of 6-7 months we will see FOUR ocean based films, all of which are almost guaranteed to make a billion world wide (BP2, Aquaman 2, Avatar 2, and Little Mermaid).
I predict that Aquaman will move to March, 2023 and BP2 will either take the spot of GOTG3 (moving GOTG3 to July and Antman3 to November) or be delayed a whole year to November, 2023 (in the currently unannounced November MCU date). The presumed occupant of that spot is Blade, but there's been no official announcement.