Given Japan's been rather lukewarm towards it even though the game has probably still performed impressively relative to the size of their PS4 base, I'll hazard a guess and say the game was in theory trying to cater primarily to as many mainstream western audiences as possible while still towing that line enough to try and not alienate Japanese audiences too much. They glanced over and saw the ubiquity of open world games littered with a seeming endless array of banal side content and decided: hey, we can do that too. They seemed to have made Kingsglaive with the express intent to try and cater to western tastes first and foremost, so it falls to reason that they were driven to do something similar with FFXV. In the end it just looks like an awkwardly kitbashed compromise of a final product to me, though one that has evidently fulfilled its mission statement given its short-term sales success so far. I just don't know if it has had any legs since.
I don't hate the game; I don't think it's terrible and neither is it on FFXIII's level. Par for the course for what I feel to be a product of too many adverse compromises, FFXV to me never clears the bar of mediocrity. It's painfully average. It's a middling experience, where any positives are counterbalanced by equally as potent negatives. Besides the soundtrack and how visually appealing it can be, at no point in the game did I sit up straight, take note and think to myself: wow, this aspect of the game is truly spectacular and constitutes a bar that future games will be measured against. I'm not convinced that what I played was a coherent package. If you told me that there were warring factions within BD5 as they were working on the game and Tabata had to do the thankless job of being the tenuous duct tape to hold it all together and to prevent full on chaos from breaking out and dooming the project there and then, I'd believe you.