So, Instagram provides an API to embed posts on it. They also have a license to all their users photos. They specifically even gave themselves the rights to sub-license these to other users. Yet, they don't actually grant the rights to those embedding their posts.
This is precisely why we need an open Internet. The current social media platforms all do their best to keep users within their own ecosystem, without access from outside. Ever tried to follow a Facebook page without an account? Or a Twitter user? Or someone Instagram? The tech exists. RSS would do fine for these (in fact, I’m using RSS Bridge to do exactly that), but more modern alternatives exist such as ActivityPub.
Both Twitter and Reddit are also closing down on their API, allowing certain features to be accessed only from their official client. Despite much better and more polished ones existing for both. Facebook has done so a long time ago already. You used to be able to do all sorts of fun shenanigans with it. Tom Scott has a fantastic video about that