Extracting moving object from background

Suppose I have a video of something (a person or a moving thing) which is clearly visible against the background, for example something dark against a bright blackground. Surely greenscreening is something like that, but how to do greenscreening (or bluescreening) I know, but what if they background is not that regular, but still does not blend with the object in question that much. Is it then still possible to extract the object, and replace the background?

Can this be done in Adobe Premier Pro and/or Adobe After effects?

Don’t know… but I guess your question is rather rhetorical to suggest it is not possible…