Except how much of a departure each entry is really depends on your point of view because FF has redefined itself for a long time, alienating a lot of fans along the way as well. Even VI with its vaguely steampunk setting was off-putting to a small group of people who wanted the series to remain set in this DQ-like high fantasy setting. Then VII came in which added a whole horse of new fans while further dividing the existing fan base. Then VIII was polarizing because it wasn't like VII, then IX was polarizing because it brought back the old which new fans didn't get, then X was relatively successful but still some fans thought voice acting had nothing to do with FF, then XI was an MMO, and the rest is history. Honestly, the older games seem pretty even only because they've gotten the time to settle in the eyes of fans. Give XIII and XV time and they'll be the same, and once XVII comes out, people will be saying those were the last games that really "felt like Final Fantasy". You can really see this going on with FFXII right now. It's just that the "problem" of it being different is way more pronounced now because the series itself as well as the fan base are larger than ever, and the gaming community in general has a much more prominent voice.

Not saying you have to enjoy XV though Everyone is entitled to have their own ideal FF in their head and hope it gets released one day. I just think that there's really no such thing as a "series standard" that involves anything other than constantly challenging the formula in various ways.