I think my biggest issue is that the AP items have mana on them.

Speaking from a jungle perspective, lost chapter sucks to build (we've seen this in history already where riot tried to make runic echoes build from it, and immediately revert a few patches later), it just doesn't give much in comparison to revolver/dirk does. Assassins that love flat magic pen would have to give up early spikes in revolver, and gold sink into a mana item they may not need (ekko and fizz currently don't go luden's on live.. but more specifically in the jungle, ekko, elise, nidalee, karthus, evelynn.. they do not want to first base a lost chapter it just doesn't do anything for them compared to fiendish, aether wisp, sheen, or revolver in the preseason's case.).

There should be more flat pen options for manaless AP users (as in ones that don't care for mana builds), as there's none in any components or legendary items now (oblivion orb is now just culling with no replacement), and the only flat pen is on luden's echoe and protobelt's mythic passive.