If you mean like, actually everything there is to do, I don't think that's possible.

Just for one simple example, you need to win a million GSP with the mini cactpot for one of the achievements. Even if you somehow won 10k every single day it's been available (and you're lucky if you even get a ticket that HAS 10k on it once a week, let alone win it), you're still only at about 220k/1,000k on that achievement.

You also can't have all the TT cards.

You also are unlikely to have every drop available from T13.

So I guess the possibility of "completing FFXIV 100%" depends on how you define it. But even getting all the achievements would be extremely difficult, and as of right at this moment, impossible.