The childish letters that occasionally drop.
I can't believe someone thought they were funny or cute.

Easter Egg items and yes, some are funny and cute.

Well, if you enjoy childish attempts at humor that is your prerogative.
It is out of context for the mood of the game where the known world is being attacked by various creatures bent on total annihilation.

Then just don't pick any of them up, problem solved.

I don't.
I wish there was a filter so I could remove them from my sight.

They are color coded as an Epic item which makes me think I am losing out on receiving valuable weapons or armor instead.

Well, it's pretty obvious they're a scroll rather than gear/weapons.

You didn't understand my point.
If the scroll didn't exist, would an Epic item have dropped instead?

I doubt it. They're not substitutes for unique items, they're just a bit of fun from the devs.