Hello Jnizzlew,
Welcome to Apple Support Communities. When you navigate to: Settings > General > iPhone Storage. Under "Recommendations", you might see a list of recommendations for optimizing your device's storage. When you tap " Review Large Attachments", tap "Edit" on the top right corner, and you'll be able to select multiple attachments to delete.
If you would like to see an option to "Delete all", you can submit feedback regarding this using the following link: Product Feedback - Apple
For more information about checking and managing the storage on your iPhone, check this out:
How to check the storage on your iPhone and iPad - Apple Support
We hope this information is useful. Kind regards.