Flickr was the Instagram of it's era. It could have maintained that crown if Yahoo gave half a duck about it
Flickr incentivized uploading a lot of photos with metadata and was highly searchable. It was great for photo hobbyists building a personal archive for others to peruse.
Instagram was for smartphone photos and playing with filters to set a vibe, and ephemeral sharing with friends and people you wanted to impress. It’s hardly searchable at all.