Sites like Reddit make money off of having it's users repost the original content of other people. While it's true that many Reddit posts link back to the original source, there are numerous subreddits such as /r/TikTokCringe that rip video from the source such that a viewer will never interact with the original creator.
In a similar vein, there are many very popular Instagram accounts that act as aggregators. They report memes, videos, and clips from others (possibly while adding a “Look at this!!” type white bar at the top) without ever “creating” something themselves.
My gut feeling is that it's a grey area – I can't find any great examples of a legal precedent, and we all know companies like Buzzfeed built empires on this type of content. What does HN think?