Why does Riot let some champions stay in the trash can for so long?

Yeah, I understand that with difficult champs like Nunu and Ryze, you need a full rework to get them on track, but why have Lucian and Caitlyn (popular champs) been casted aside for months now? Why has Viktor, a former popular champ, been garbage since early season 7? Even Galio who was just reworked with a VGU and everything was just left to die after his AP buff failed.

Yes, I know it takes a while to test and figure out what exactly to change, but the champs I've mentioned just need a nudge in the right direction, nothing that can't be figured out in a month or so. So I really don't understand how we can go more than 2 or 3 patches without some attempt to nudge these champions up a bit in winrate.

A lot of the times I see champs that are middle of the pack getting the buffs to push them into the meta, but sometimes that just makes them OP and now they have more problems. When it would've been a better use of their time to buff the champions that really need it in the first place.