Optimizing your media library is one of the quickest wins for site performance....

https://alpha-wiki.win/index.php/WordPress_Generates_Medium-Large_768_px:_What_Is_It,_and_Why_Is_It_Eating_Your_Storage%3F

Optimizing your media library is one of the quickest wins for site performance. Start by naming files descriptively so search engines actually know what’s there, then include helpful alt text for accessibility