I think the issue is, when you're making entertainment that targets a more broad/casual market, following a formula doesn't "poison" the well nearly as quickly as people think. Consider all the big gaming franchises that release basically a slightly-different skin of the same game year after year after year to colossal sales, or how Hollywood is focusing on "cinematic universes" that are basically sequel after sequel of very similarly-structured and themed movies. Yeah, obviously, eventually people tire of the formula and move on, and there are some misfires along the way, but how long do they expect this game to last anyway? Are they going to have 5 more years of active content? 10 more years? By that time, how much will the gaming world have changed, and what will the newer younger generation of players want/expect?

It's very easy to make major changes when you have something that's clearly broken, as happened with FFXIV 1.0. But since 2.0, the game has gone from success to success, with 4.0 being the most successful yet. I don't think they're under any delusion they'll be able to keep that up forever, but what's riskier? Sticking with the formula you know that has brought you success so far (knowing it won't work forever and will taper off), or taking things in a different direction that may or may not be as successful but breaks the status quo? I dare say that 95% of companies will choose the former, until there's very clear, undeniable signs that the market has changed (and then they'll follow the market to whatever's next).

All in all, I think the developers feel a great weight of responsibility -- now that they did turn FFXIV around and make it successful -- to not screw it up. And this is leading them to be rather conservative in continuing to follow the "winning formula." It's natural that places like the Forums, Reddit, etc. will tend to attract people who are the most invested in the game and have the strongest opinions for change. They also know full well that they can't please everyone, and that any major change they make disrupts the development cycle and comes with a trade-off. (People act like it's just a matter of throwing more money at the problem, but opportunity cost and the impact on other stable processes are the much bigger issues.)

If anything, I think the flaw -- such that it is -- is that the game will continue to "show its age" as time goes on, and so the number of times they have to explain that they're limited by the underlying engine/servers/code/etc. will keep increasing. People want some sort of sign that they'll invest "whatever it takes" to overcome these limitations, but that comes down to a broader business decision about whether to continue to push FFXIV, or to start work on "FFXVII Online." It may be a few years until we have that answer, and there'll continue to be uncertainty in the meantime.