Aside from the fact that apartments are, functionally, still not as useful as having a house (as there are mechanics gated behind an FC house); a lot of apartments were snapped up by people who owned FC plots and private plots already. People want rooms, they want apartments, but they can't because most of them are taken up by greedy people who already have FC's, private plots and apartments and want more and more and more.
The way I see it, there are three solutions. One, the least likely of all, is that they just add more servers until everyone can have a house. This will never happen: the game keeps getting bigger, servers are expensive and there's a shortage. Square also has shown almost no interest in this despite having had literal years to do this and the problem only growing exponentially worse. Two: instanced housing. Give everyone their own house in their own private plot. If they care so much about neighborhoods creating that lived-in vibe they could let people choose who their neighbors are so the game will load up your friends houses or whatever when you leave your house to hang in your lawn and you can visit their house like you would an apartment (knock at the door, instance into it) so people can decide if they want to live next to their best friends, the coolest looking houses - or just live alone. This even allows for a brand new avenue of revenue and itemization in the form of customizing our private plots, taking a page out of PSO2's housing system! Add a new item - let's call them memory crystals or something. You shove one in to your private home's little allegan terminal or whatever and suddenly the terrain looks different. They could use this as a means to add unique styles and designs during events, story missions or even on the mog station (I'm sure people would pay a good few dollars to have their home plots look like nice renders of their favorite FF locations...) Finally, and most radically of all, the third solution is to simply limit housing. Account-wide one plot per-person. It is absolutely dire that we're at a situation where some people can own entire wards, that people who already have plots are vastly more likely to be double or triple dippers while the vast majority of players can't even get a single one. If square can't get their shit in order the least they could do is straighten out their own janky mechanics on this front, set a date and reimburse the players for whatever plots they have to give up.