You're not the only one let down, let me tell you. Like Reinhardt said, they forced a self-fulfilling prophecy. There was no merit to the idea that "Blue Mage would not work in XIV as it did in XI," for the very reason that the claim exists at all. To acknowledge that XI's iteration of BLU could not work in XIV is true, but we already know that. They're fundamentally different games. Anybody willing to both see and accept this fact would have accepted a less free-formed implementation of BLU as a full job, and those that wanted XI's version, well, I guess they haven't gotten the memo.

The devs COULD have made it a full job, given it a set of starting-tier skills you learned through the job's initial story quests, and had later skills learned as you level with inspiration taken from characters met and enemies faced during MSQ encounters. The entire "how" of BLU could have been that the knowledge of abilities we've seen in our journey were always in our minds, and that the Soul of the Blue Mage and use of blue magic allowed us to recall these and wield them ourselves. The system of going out and learning from encounters in real-time wasn't necessary at all.

For whatever reason, they refused to adapt the concept to the game they wanted to implement it into and left a hell of a lot of people very whelmed.