Since around 2019 or so was when we first figured we'd have the game done, but unfortunately;
This happened, multiple times over. For future games, this shouldn't be as much of an issue because we've refined our workflow and we've learned much, much better what stuff will take far longer than expected and, most importantly, to not give release dates until the game is 99.9% done.
But this happened mainly because often, when we introduced something new to the game (more on that in a second), we ended up finding out "oh, shit, this particular feature or mechanic is how we expected it to be for the most part, but there's this one part that's kind of buggy/doesn't feel great to play/is way too hard/is way too easy, so we need to adjust it some".
And then THAT would turn into "ok, so we adjusted it, but NOW it's got THIS issue with it, and now it's got THAT issue", and so on.
The other issue that comes with a small team like ours (one programmer, one artist, one writer/level designer, one musician, and one sound engineer) is that if one of us is "knocked out" (sick, away with family, etc.) or burned out or is struggling with some particular aspect (ex. programming not operating as expected, can't come up with a good concept for art for an area, plot hole that needs to be fixed), it can slow the other people down because we're all dependent on each other's work.
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For example, if Frouge wants to program a boss, he can do the very basics, but to do anything beyond that would be a waste of time if he doesn't have the art to go with it, as he might make a hitbox for an attack far bigger than the eventual art for the attack is, for one tiny example among many.
Or if Triangulate wanted to make an enemy, but I haven't given him specifics yet about how I wanted it to be integrated into level design, then he can't make the enemy because he needs that info.
And for yet another example, if I wanted to write about the backstory/culture of an enemy in the game, I can't do so until the final art, attacks, etc. are in, because otherwise I could write up some big backstory about say, aliens that toss snowballs at each other with bombs in them, and then the final attack for the enemy ends up being laser beams only, making all that writing and time spent on it go to waste.
As all design/gameplay/art/audio/writing etc. choices in the game need to be decided by our team democratically (2 out of 3 votes for the main team), it can lead to a lot of refinements/compromises with some stuff in the game, which ends up being a time sink in some cases.
But we didn't want to make a game with the setup of "one person is the boss and what they say goes, period", because that kind of setup is so prevalent in games/movies/tv/media that while it gets things out the door and it gets things done, it also results in a lot of people just being used as "cogs in the machine", and that's the last thing we want.
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To go back to what I mentioned earlier about "new content being added" though;
This has never been the case. There's a document from February 2015, back when we started on this, that already has all the levels outlined, with general mechanics, enemies, etc.
We've swapped some mechanics for others (the Ice Level used to have bridges you break as a mechanic, we swapped that for the laser puzzles), and we've of course added in a few things here and there, but for the most part, probably 95% of the game's main features/mechanics/content etc. was decided within the first few months of development and hasn't really changed much since then.
You're definitely right there, and that's with teams of sometimes 100+ people, and $10,000,000+ of dollars of funding behind it (not counting marketing funding), operating under the "you are a cog in the machine" principle to just grind out content regardless of how much passion/quality is actually in it.
Spore - 8 years
The Last Guardian - 9 years
Too Human - 9 years
Team Fortress 2 - 9 years
Final Fantasy XV - 10 years
Prey - 11 years
Diablo III - 11 years
Mother 3 - 12 years
Duke Nukem Forever - 15 years
For the record, Future Fragments is currently at 7.5 years.
We have to release by the end of August at latest. We want it out sooner than that, but it's coming out no matter what state it's in by then because September-December is a death zone for games, and we literally can't afford to wait to January, because we'll be broke/maxed out credit cards by October at best.
I realize that's contradictory to what we've been saying about wanting to make sure it's in its most finished state, but we just have no choice financially. So we're working nonstop to get it out by then, we hired the second programmer we mentioned earlier, along with other things we've done to speed things up even more.
The first month of release will be a lot of fixing things up on our end for anything left we've got over if it does take that long, but worst case scenario, it should still be in a 99.9% completed state if it does take that long.
The main focus we have right now is just to make sure all the core content is in before release, then spend the rest of our time polishing/bugfixing.
Still, even with all this, I think that much like some of the games on that list, FF will turn out to be worth the wait/delays.
(There's no way in hell future games will take this long, though.)
