Hello Newtan,
To edit any theme files, please build child theme first. You shouldn’t edit any theme files directly, as when you update the theme, all your edits will be reverted back to original. So, to be safe always build child theme, you can download the sample child theme ( https://catchthemes.com/blog/create-child-theme-wordpress/ ) and then you could go to the inc folders there and open the clean-journal-featured-slider.php . Then find and copy the whole function clean_journal_page_slider( $options ) { function and paste it in the functions.php of the child theme.
OR you could use the pro version and use the featured image with no link to remove the alt text and also use other features of the PRO version. You can follow this link for more information.
https://catchthemes.com/theme-instructions/catch-responsive-pro/
Regards,
Bplv
