Why your own posts are the hardest ones to get back
Every platform is happy to store your work and reluctant to hand it over. TikTok's Save video stamps a moving watermark across your own footage. Instagram's bookmark is a pointer that dies with the post. Facebook saves to a list inside Facebook. None of them give you the file.
ClipKoala fetches the original the platform serves before those layers are applied, so a TikTok comes back clean at the resolution you uploaded, and an Instagram carousel comes back as separate full-resolution files plus a ZIP of the set.