You can get sort of a preview by going into visual mode with 'v' and then typing in the motion command, and once you are happy with what was selected you delete the visually selected text. I agree that its not very consistent here, because for a regex replace you would use a /c instead to get confirmation.

Regarding the 'I pressed the wrong key' problem there is undo (and if you enable undofile you can undo even after saving or reopening the file), and there is git history.

Having said that I agree that there are often situations where automating something (or using a more complex Vim command) would take more time than doing it by hand.