This is all on the nose.

Tanaka decided FFXIV needed it's own version of the job system with totally unique jobs in their attempts to separate FFXIV from FFXI. When Yoshi-P stepped in, these new classes not aligning with the beloved jobs of FF canon was one of the first bits of 1.0 weirdness brought up.

So, they just looked at which class could most easily be "upgraded" into a FF job and went from there. In fact, arcanist was in 1.0 as a not yet implemented class option. I guess they felt like this trend was required in 2.x as they made Rouge/Ninja the same way way, breaking the hearts of players dreaming of a Theif class the world over.

Just, please, based Yoshi-P, make Geomancer playable in 5.0 or earlier. Please.