Have you accidentally set a load of values at store level and not on the default level?
Have you been rationalising attributes leaving values unused?
Have you been getting errors when adding images or have unused images in your media folder?
A great little find and a wonderful tool here that helps to resolve these issues
https://github.com/magento-hackathon/EAVCleaner/tree/magento2
Commands
eav:config:restore-use-default-value
Check if config admin value and storeview value are the same, so "use default" doesn't work anymore. Delete the storeview values.eav:attributes:restore-use-default-value
Check if product attribute admin value and storeview value are the same, so "use default" doesn't work anymore. Delete the storeview values.eav:attributes:remove-unused
Remove attributes with no values set in products and attributes that are not present in any attribute sets.eav:media:remove-unused
Remove unused product images.