Ugh this destroyed my productivity too for a while. I even wrote an entire blog post about my woes and different experiments to get back to getting consistent shortcuts across terminal and GUI apps here: https://alexdav.id/2020/07/12/text-manipulation-and-modifier.... GTK key themes didn't end up working out for me, and I ended up with a custom QMK solution, but it's not great.

Note for people still using macos, you can enable many more readline shortcuts by creating a special file at ~/Library/KeyBindings/DefaultKeyBinding.dict. I made a repo that simplifies the process to just a single git clone when setting up a new machine: https://github.com/alexdavid/keybindings