I mean rugby also many plays and routes to remember.....
But I do agree that NFL playbooks are particularly thick, because that's how the game has evolved. It's so stop-start, and because each play takes place from a dead-stop, that gives coaches the chance to run plays every single time. The whole thing is so controlled by coaches and offensive/defensive coordinators.
Rugby is also very strategic, but it is also much more organic than NFL. Teams play within an overall structure which provides the basic shape of play; pod-systems, attacking patterns, support runners and so on, for example 2-4-2 or 1-3-3-1 formations would be the two most common. Play doesn't stop every time, there is a continual flow to the game...these formations and systems provide the overall structure, but there are multiple options within this and a lot of decision making based on what happens in the game.
When play does stop dead - either from a knock-on (fumble to yanks), or from going into touch (out of bounds) - then there is the option for strike moves. As in NFL these will also have various cryptic names and calls so the other team does not know what's coming. In high school we had plays with calls like "Ocean 13 left" etc. If a scrum happens and the number 10 (fly-half/out-half, the rugby equivalent to a quarterback, the player who makes the decisions and sets the tempo) shouted that call you would need to know what position you needed to get into, what line you need to run to hold the defender in front of you. Usually this will give the 10 multiple passing options depending on how he reads the defense in front of him (are there players out of position, whether it's a blitz defensive or drift etc.). Sometimes as a runner you know you will not even be getting the ball on a particular move but you need to make the run/correct route with full conviction in order to sell it to the defense and hold the defender in front of you. There are a lot of moving parts. Just like in the NFL.
I have already posted a video analysing one particular move, but here's more examples:
@WandySaku2 this may interest you as well