Black Mage and Summoner change a lot during expansions and latter gets a rework for Endwalker.

Still playing caster is a different experience and view vs a Ninja but stick with Red Mage just to have the grasp of it. Simple job, lv50 with most of the basic tools already and only gets more stuff the further you progress.

For Astrologian you really have to bear with it. Try get it to lv50 at least, the job feels very awkward under it but later it gets more skills and traits that should smooth the runs