If you have a free character slot, imo it's definitely worth rolling a brand new one and starting over, as a way to reacquaint yourself with the game. Or yeah if there's a low level character that you started but didn't do much with, it might be worth deleting and starting over.

Plus a new character will have access to all of the quests and the main story again, which you could be locked out of on your other characters if they'd done the quests already.

I would hang onto the more established characters - certainly the one who's a crafter (it's a slog to level all of that stuff up again), and perhaps others who have already leveled up skill lines that can be annoying to level, like mage's guild, psijic, antiquities, etc if applicable.

As Soarora mentioned, you can always use the armory system to reset a character's skills / cp / attributes without actually deleting the character (and depending on how long you've been gone, you may find some of these things have been reset for you already - I know CP was reset for everyone at one point).