You should only be able to delete tables from plugins that aren’t active.
According to your screenshot, wp-optimize doesn’t detect the Smush plugin as installed.
My guess is that the plugin folder was renamed. WP-O uses the plugin’s slug (wp-smushit in this case) to detect if the plugin is installed and activated.
Also…. you’ve previously made clear that you don’t want to hear this, but because the WP core developers have stated that they consider no table prefix to be a broken, unsupported configuration (and one that’s impossible to create using the built-in WP installer), that’s not a setup we test or support ourselves. I notice in your screenshot that none of the tables have been labelled in terms of their owners (no owners detected); that might be related.
