I've seen multiple posts on here (and even some professional reviewers) talking about how you can't pick actions for your party members in battles. There's actually a very simple fix for this. At the beginning of a battle, on the screen where you have the option to fight and flee, you can choose Tactics. In that menu, you can set your party's tactics, and one option is to make your characters Follow Orders.
Now you can select their actions like you're used to in a turn-based JRPG.