You are probably refering to FF Xv, as I don't remember 13 doing super well, and 12 didn't do better than X.(I think).
That's my point. People have been arguing that FF lost its identity even back then when FFX did away with world maps, airship piloting, some series tropes, and the utilization of voice acting. Or because of the designs. It's one reason or another.
Despite any of that, it did extremely well. Those criticisms were in the minority, and the series continued to grow in popularity.
Now the focus of the argument has shifted to turn-based vs real-time, even though Square-Enix still makes turn-based FF games to this day among hybrid and action-based battle styles.
The problem is that XV did most of its sales on the long run, and did so at lower prices, as it hit something close to bargain bin prices relatively fast. Plus, and I might be mistaken on this, FF XV developmemt cost was especially high compared to previous FF, so much so that even some DLCs had to be cancelled because it lacked interest for them and Square decided to cut its losses. Not to memtion the critical reception the game had. So all in all, it's financial success might have been lower than what any of the previous entries might have been.
FFXV had a troubled production going all the way back to FF versus XIII, prior to its reboot. The project was in preproduction for almost a decade before being rebooted into FFXV.
Followed by the switching of game directors and cutting of content to get the game out. Resulting in some of the original features being implemented retroactively after the initial launch.
The critical reception of FXV was less than some entries for sure. Even so, the game ended up selling well and made its development cost back.
FF XIV is an exception. And even then, an expensive exception that was very costly Square with its 1.0 release. I personaly don't even consider the MMO entries an mainline games, as they are an ever expanding story, but that's a discussion for another time.
XI and XIV are in fact mainline entries regardless of what you feel about them. This again is another point to my argument about how some FF fans have differing opinions and views of what defines Final Fantasy because of "reasons."
FFXIV had issues because of how bad it was in 1.0, that's pretty self-explanatory. A badly designed game is a badly designed game and the reception will more or less reflect that.
A Realm Reborn relaunch and the subsequent expansions completely turned it around and made it one of the most commercially successful FF entries to date.
So yeah, FF has been a hit or miss for almost 20 years now. And even the ones that are a hit, the "growth" we see is small compared to what the other long standing franchises are doing nowadays.
FF is a hit or miss depending on who you ask. Growth is still growth. In other words, not declining or stagnating.
