I think people are leaving the game simply because the people who used to play all them years ago were mostly teenagers etc, and the game has been out for many years. The people who started when they were 13 are now into their late teens or 20's and consequently have other commitments than gaming. This on top of the fact that FFXI has a lot of other competition, which have a lot more advertising than FFXI, and the fact that FFXIV is just round the corner has led to a decline of the overall population. New players aren't joining as much as they used to so SE have to make up for that by introducing ways to lvl fast but the population is still declining.

So basically to sum up - FFXI is suffering from old age, and I personally think the impact that Abyssea has on the game is in no way relevant to people leaving. The level cap on the other hand was, but that was a long time ago and people left before they introduced it. People just play the "blame game" and Abyssea is an easy target due to being so different. Of course nobody can really know because nobody submits a survey when they quit this game, so like every argument on here, it's just speculation and opinion, but seriously people - stop blaming Abyssea for every wrong in this game, there are a lot of other reasons why things have gone wrong and a lot of things that have gone right in the game since.