So... What Exactly ARE the PS3 Limitations

[Lambdafish]

The best way to answer this is with Yoshi P's official answer to your question:

Question: How long until you drop support for PS3?

Yoshi P: "That will depend on how long people continue to play on the PS3, I've mentioned in the presentation this morning that I want to make sure that "FFXIV continues to innovate", and there's certainly the possibility that whatever innovation we seek will come with certain technical requirements. For example in EQN, which I mentioned earlier, it would not be possible to realize certain things like physic-based gameplay without meeting the hardware prerequisites. So if this becomes something that players want and we start to see people leave for rival products, then we can not just sit around twiddling our thumbs either. After all, we too need to ensure we have the necessary weapons to take on other MMORPGs in the future.
For example, if we were to have a large-scale FATE where players can ride on a flying mount and freely fly around and swoop down at a dragon that is 200 meters long, players would probably be impressed and entertained. However, it would also require us to raise the minimum requirement when it comes to hardware specs.
Our aim has always been to develop the game so that players can have the same experience no matter which hardware they play on. However, if we were to become too fixated on this and become unable to innovate, then this will cease to be a FF game. So I do not plan to say that we will support the PS3 version forever. At the same time, I'm not saying that we'll be ending support by next year or anything like that either, so do not worry."

Now granted this is from an old interview (2014), but it does describe the kinds of areas that the devs are limited in, and have always been limited in since the game launched.

Source: https://www.reddit.com/r/ffxiv/comme...p_features_of/

As has been pointed out, PS3 can only display a certain amount of things on screen at a time, and Yoshi P references spectacle and open world events as something that is not possible due to the limitations, but there are many more things that it gets in the way of (I believe UI is a big one)