The new WordPress 5.x has set the block editor as default one.
If you don’t like it, and you want to switch back the classic one, you can easily follow these steps:
- go into Plugins->Add New page
- look for the Classic Editor plugin.
- install and activate it
As you will see, it will add 2 new settings to Settings->Writing page to switch classic/block editor as the default one.
PS: you can reach it also from the plugin’s Settings link.