In plain language
Anything operated by dragging needs a click/tap alternative.
Who it affects
People with limited dexterity and switch, eye-gaze, or voice users who cannot drag.
How to check
Find every drag interaction (reorder, upload, slider, map): confirm you can do it with simple clicks or a menu instead. Worked example — A childcare-booking service's scheduling page: try panning a map using on-screen pan buttons or keyboard arrows instead of dragging: if only drag works, it fails.
Common misconception
A drag-and-drop file uploader or reorderable list feels modern, but without a button-based alternative it locks out anyone who can't perform a precise drag gesture. Real example: on a hospital's patient portal appointment scheduler, something must be dragged to operate it and there is no click/tap alternative (no 'move to' menu, no buttons).