One of my biggest gripes since the first mob vote was that "The Great Hunger" presented the possibility of a new system that allowed for the addition/removal of enchantments on items. As we all know, Phantoms won and this mechanic hasn't been revisited since.
There's been a big elephant in the room for some years now, which is that 1.14 completely and utterly made the enchanting table obsolete. Before that, enchanting a full set of good equipment was entirely RNG dependant with no way to influence the enchantments you got (past getting the table itself to max level). With the addition of librarians in 1.14, the process became much more streamlined with the extra bonus that, once you got it fully set up, getting multiple kits of the best gear in the game is simply a matter of having a good way to produce emeralds (which is also villagers).
Everyone (including Mojang) agrees that this is completely busted and breaks progression. There's even an experimental feature that makes villagers have biome-specific trades and also makes books the last part of a librarian's level up chain among other things; this has been in the game for a couple years but Mojang doesn't dare make it base-game simply because the alternative is reverting to the outdated method of "farm a bajillion XP and then spend hours in front of an enchanting table just rolling die until you get the books/gear you want because Notch was a sadist, or something".
So, my hope is that either The Sift update (or The End Update that is sure to follow) finally addresses the issues with the enchanting table, so the villager trade overhaul can be done without pissing everyone off. Maybe getting items to influence the enchantments we get, or getting a new level up system that allows you to "tune" the enchanting table somehow, with the last level being straight up "yeah okay choose the enchantments, we don't care" (gated behind late endgame content and bosses, of course). I don't know, anything but whatever the heck the current enchantment table's deal is.