Description of the need
Many end-users today do not expect to have to "prepare" images before uploading them. They should be able to crop, rotate, flip, etc. images after they have been uploaded into a system. The "art" of even manipulating an image prior to posting is unheard of to younger audiences, when the primary feature of many photo sharing tools is last minute manipulation on an image through an app or website.
After uploading an image, you should have basic manipulation tools available to modify that image. I think a tool like https://fengyuanchen.github.io/cropperjs/ provides a good basic set of functionality for crop, rotate, and flip.
An additional library (or a more comprehensive one) that also provides filters may also be desirable, such as http://camanjs.com/examples/ but that one in particular is no longer supported, nor is it a GPL-compatible license.
Alternatives that have been considered
We could always leave this in contrib. Both of these modules exist for Drupal
Ideally you'd be able to edit an image both immediately after uploading (such as in a dialog) and after uploading from the File management listing (admin/content/files). Perhaps initially we should just worry about one or the other, with the file listing option being the easier one because it would probably just get its own page.