Deleting WordPress theme through File Manager
If you do not want to use FTP/SFTP, there is another option, File Manager, through which you can delete the WordPress theme. Its process is just the same as FTP/ SFTP client.
In this process, first, you have to log in to the hosting account dashboard and then visit the file manager option in the Advanced Tab. Every hosting company’s dashboard is different, so look carefully for the file manager option in your settings.
After logging in, you have to go to the/public_html/wp-content/themes/folder, and there you will find the themes you have installed on your site. Now, select the theme that you want to delete and right-click on it; a shortcut menu will appear where you will see a delete button, press it, and wait for the confirmation tab. You will see an OK or Yes option in the confirmation tab, click on it, and your theme will get deleted.