> Pressing page-down on a text-page or in a text-editor, without animation, it takes me a lot of time and energy to find the place where I left off reading or editing before scrolling.

We used to be able to look at the scroll bar to keep track.

Furthermore page down/up used to move a full page consistently. But today it might as well be a random amount specific to the application or content. Making it impossible to train muscle memory.