I hate it when devs say we have to make what we want of the ending. It is very lazy storytelling, IMO.
Well that's just straight up not true. I mean most of the ending is pretty clear given context clues and themeing. The parts that are ambiguous are meant to be that way to give the viewer a sense of agency in how they perceive the characters and what they deserve or what the viewer feels should have happened. It fosters discussion but doesn't lessen the impact of the end. Lets not even get into the fact that having "the word of god" can very well ruin otherwise great scenes that have purposeful ambiguity.
Like, look at SoTC. The ending is kinda weird and confusing and we need to really think about the implications and the situation and to have a bit of thinking in order to kinda sorta make a connection to Ico. But its in no way a bad ending, nor was it lazy storytelling. Hell i don't even think people are annoyed that we still don't know what the wanderer and girl's relationship ever was (Because, as it turns out, that wasn't important)
As for the ending of 15, not giving us a post script for the bros is more powerful than saying "OH THEY GOT OUT OKAY" because, we don't know and shouldn't know that. We are left off with noct talking about how he leaves it all to them, and then they leave and he leaves and that is it. We don't know if they made it or if they will do anything or anything because that's not what's important in the scene.
imo, the ending of 15 gives us all the important bits well. It doesn't give us superfluous info we don't need. When handling storytelling, you need to know what matters and what doesn't in a scene, and with 15, the ending is one of the few moments in the game where everything that is important is shown and talked about and handled well, but the unimportant things are clearly left off. Having ambiguous bits isn't lazy storytelling if the ambiguous bits enhance the discussion and never get in the way of the themeing or development of what happened.
The storytelling in FFXV was imo in general lazy...well, maybe not lazy, but incompetent.
They had such a great setting with Eos, an interesting lore/backstory with the 6 gods, the Starscourge, Ardyn and the Lucis Caelums, such a likable and relatable main cast with the 4 bros and a promising game story premise. They squandered so much of that.
Outside of the cut content, my big issue with the narrative of 15 was that a LOT of it was stuck to newspapers and radio reports. I clued into this early and got a LOT more out of the story and world because of this, but the vast majority won't. How important the hunters are, Ravus' execution, knowing that the empire uses ancient tech, luna's various childhood radio talks, etc. So much back story and world events are stuck to voice over and papers and....
Well lets just say that while I love that kind of story telling for additive effect, 15 takes it to the point of being almost mandatory and the main plot-lines suffers for it.