IMO Ogre Bone is definitely worth feeding to a slime
Avian Feather and Luck I think you're wrong about, but to be fair it does take two things to make it good.
First, you need to read the book that turns your Lewd Knowledge into MATK.
Second, you need to use that one mental change machine to transfer your Luck into Lewd Knowledge.
Luck being the least useful stat makes it a prime candidate for reduction, and using that machine repeatedly also helps with corruption management.
I think that those worse items are not really bad and actually the game is decently balanced. I define "bad" items in terms of if I keep them the longest in my inventory without using them or when I want to sell items for money, those are the first ones I think of selling.
Ogre bone is good if you use your slime as a punching ball for enemies, but sometimes you might want your slime to strike fast and even before aura actually (With the spell book for lightning) so loss of agi can hurt. I understand why people don't like this item.
Avian feather would be a very strong item if slimy fluid did not exist, but there are a lot of it. So I get a lot of agi anyway and this item will stay on my inventory for a long time due to that. Yeah that is also what I do with the interaction of lewd knowledge and that mental change machine, but I don't touch this item until then for sure (and usually I finish the current content of the game before that).