Many students rely on catching punches (which isn't necessarily fine motor skills, but still difficult), hand positioning, etc. Aikido does require to a degree, some dexterity which from what I've read and experienced, can be destroyed in no time. .
And no disrespect intended to you, Logan - you have started a worthwhile thread.
Re catching punches: I've been a student in several dojos from different lineages but one commonality has been that each one emphasized NOT catching punches and a lot of effort went into getting newbies to not develop that habit.
Re fine motor control: just trying to be accurate in definitions.
I have arthritis of my thumbs + two ruptured extensor tendons in one hand, so at times my grip is very weak. This does NOT affect my fine motor control, which is the dexterity more than grip strength (the classic therapy for people needing to improve fine motor control is sorting colored beans). I can always do some detailed hand sewing. However in the dojo I can often not do a classic nikkyo on an attacker - that's not fine motor control, that is the ability to close one's hand.
But the principles of aikido should not depend on a specific hand grip, just as self defence should not rely on pre-deciding what technique one is going to do in two minutes.