You should try
SimSports.net. Admittedly, I enjoy making custom playbooks, but I feel like this made it much easier than doing it completely in the game. Putting it together on this site allows you to easily look at any formation and see all the plays in each formation at once, instead of scrolling through. I feel like it wasn't quite as overwhelming and tedious this way.
That said, getting to the point of having a full playbook and still feeling like there are plays I want to put in can be pretty frustrating. It's best to start out with a clear idea of what type of offense/defense you want to run. I run the spread option, so my formations are limited to all Shotgun and Pistol sets. Then, with each of the formations I settle on, I start with the option plays in the formation and work out from there.
I totally understand the overwhelming feeling, but for me, I'm very picky, so a custom playbook is the only way I'm going to be able to get close to having a playbook I'm really satisfied with.