We may enjoy all the bells and whistles that come with Gutenberg, (the new default editor in WordPress 5.0) on the other hand, many websites probably won’t benefit from the new editor. Furthermore, you may need to restore the classic WordPress editor for compatibility reasons or just because most of you are already familiar with it and they are not very keen on learning a new way to work.
To activate the Classic Editor:
Go to Dashboard > Plugins. Then activate the Classic Editor plugin.