I feel like I'm missing some tactical choices about my character. Actually I'm so lucky I've chosen the only class with 2 jobs (arcanist), so I have chance to change my gameplay a bit but really, there isn't a difference from me (summoner) and another random summoner.

No choices. Secondary skills are just cooldowns that may be used on correct moment and everyone have access to the same skills (which are indeed 5... so, no choice at all, just level farming).

The character doesn't involve any tactical choice.
Yes there is the option to actually DON'T use a job (loosing a lot of dps anyway), but you'll get a lot of skills, which are just cooldowns, nothing that changes your character a bit.

And I'm so lucky I can switch job.

When they said you can take skills from classes I imagined you can also take PRIMARY skills, no they just give you illusion of it: you can take thunder as an arcanist, but that won't work on any of your spells, basically being just an additional dot.

The only game-changing spell is getting a heal with thaumature, changing your gameplay a bit since you can heal.