I just want to note that the way SE markets KH is not the same as how they marketed FFXV. Comparisons can’t really be drawn between the two.
Yeah, even if we don't look at XV's history in itself, Final Fantasy is a legendary brand that's been around for decades. Even though people might've thought FFXIII was poo-poo, there's always going to be a crowd to form just on that alone. Kingdom Hearts is just getting mainstream recognition and isn't the most accessible series to jump into. They're both different beasts and can't be marketed the same. Fanbases overlap, but it's apples and oranges.
It'd be a dream if SE treated KH at the same level as FFXV xD
But honestly, FFXV had a lot to prove, and the Lumimous Engine team knew they had a lot to prove (and had the DLC qualifications chosen provided before launch) but Kingdom Hearts has had this known for over a decade now.
Honestly, we need to look at the Final Mixes and be THANKFUL that we aren't stuck in that time period. I feel that new members don't realise that us long term fans had to wait over a decade to get additional material for the game. Three months since E3 is nothing compared since the 12 years since KHII.5 and longer since KH1.5
All things considered, it's a miracle FFXV even came out the way that it did. It's not the perfect game, and years from now, it's probably going to be the most interesting game in discussions development-wise, but really and truly? That game could've ended up way worse.
That's why when I see fans crying about the wait for Final Mixes, I can tell that more often than not, they're newer fans. And there's nothing wrong with that, not trying to be the OG fan elitist. But, they'll come to that realization very soon because once KH3's DLC drops, it's gonna be a few more years until the next big title drops. And I really wouldn't want them to milk Union X until then, unless they do a console version similar to FFXIV and let fans feast on that for a while.
Back in the day, you had to actually BUY the KH2FM+ game in order to play, as well as a Swap Magic package for PS2 or had your console modded. PS2 Emulation back then wasn't anywhere near as functional as it is today, so it was either that or you buy a Japanese PS2. Same with BBS Final Mix, cause I don't think we ended up getting that one either until the ReMIXes. New fans are lucky. I still remember the drought between DDD (original 3DS release) and 0.2/KH Chi/Unchained.