[Spira]

Barriers to entry can hardly be cited as the reason why any core FF shouldn't be regarded as one. In the first place, when FF transcended from PS1 to PS2, the cost of the PS2 was a barrier to entry, just as the HDD for PS2 was in the case of FFXI. When FF13 hits the PS3, are you going to cite 'high costs of console' to reason it as not being a true numeric FF? FFXI is also available on the PC anyway. With it being available on the XBox360 as well, there are virtually no barriers to entry if you own at least 1 next-gen gaming console or a PC. There is no excuse.
Cost can only be a factor to the number of people who play it. It however, cannot qualify if it as true FF or not.

In any case, perhaps many FF fans have skipped out, but at the same time many of the fans have actually taken the effort to experience XI. FF has also gained thousands of new fans through this series entry. I don't know why people seem to think FFXI is some horribly unpopular game. Its making the most money for Square-Enix amongst all its games, did you know?

In any case, when have I mentioned that feeling FF is about being D&D style? That is an assumption on your part. It also leads me to believe that you really don't know what you're talking about here.

The Final Fantasy style that is prevalant across the series incorporates 1 main element, ie. the crystals. FFXI is definitely more true to the franchise because its story revolves around the great Crystal that was sundered for Vana'Diel to be born, and the 5 mothercrystals later on. VII, VIII, X and XII have none of these elements. You could argue about the validity of nethicite, materia and spheres as being crystals, but because they have never been explicitly mentioned as crystals, they aren' the same thing. With FFVI, crystals do not exist, so you're right that I could rule VI out too.

FF is also a mix of modern and traditional fantasy elements. Airships are one of these core elements. Chocobos have become one of them. Advanced robots or magically animated objects as monsters have always been recurring monsters in the series. Don't forget DeathMachine or Omega.
If you're looking towards more traditional FF, theres also the fact of the job system. Red Mage, Dragoon, Summoner, Blue Mage.. these are FF-specific staples now.

Finally, if you think that FFXI doesnt have robots, flying castles or airships... I still say you don't know what you're talking about