Actually the gating of new jobs / etc behind Ishgard access is a pretty smart move from a business perspective and one that is fairly common as far as MMO's go. For players new to the game it actually gives them a goal to play for, something that they will have to spend time (a few days to a few weeks depending on playstyle) on achieving, which in turn prolongs the life of the content.
By now most people interested in buying the game will have seen the promo shots and videos of Dark Knight, Machinist, and Astrologian, and for some that may have been the push they needed to buy the game + the expansion. When those players log in and actually SEE other players running around on those jobs it will keep the hype going and act as an added incentive to level up and make their way towards the expansion content, also last i checked there isn't any gate to starting the game fresh as an Au Ra so they get to play through the entirety of the MSQ as the new race if they wish to.
This isn't the old days of MMO's where leveling your first class took months on end of constant play, one can easily and realistically get to 50 and complete the main scenario in a week or so at a casual pace, and with the number of people catching up / leveling new jobs the queues are likely to be decent with all the returning / new players.
This approach also prevents an over-saturation of the newly released jobs, as its fairly obvious we are going to see a large (possibly temporary) shift of older players trying them out, but with brand NEW players still playing the first set of jobs it ensures that we still see some job diversity as they make their way towards Ishgard so in a sense it makes sure that every job is still being played.
And lastly from a server perspective this ALSO ensures that every single player isn't spamming the new zones / instances at the same time, it creates a sort of staircase of access as players make their way up through the content, you wont have EVERY single player trying to enter Ishgard at the exact same time when servers go up. Sure you'll have a large number of players exploring the new areas etc but this ensures that areas like Thanalan and La Noscea are still filled with people actively doing quests and FATEs.
I can understand the feelings of someone new who very much has the "That looks cool! GIMMIE GIMMIE NAO!" perspective, but for many, many reasons gating the content they way they are is the best (and smartest) decision they could make.
If the concept of actually PLAYING through the game to reach new content is such a turn off for new players, then perhaps MMO's are not the types of games they will like in the long run.