Much of older science fiction doesn't connect with readers that have read authors that are better technically in the writing craft. Also many of the themes and "science" hasn't aged well. The best vision of the Foundation universe is Donald Kingsbury's "Psychohistorical Crisis". It is more up-to-date and crafted well as a large novel.

As a side note, the one author that has built a multi-book "Future History" that I recommend is John Barnes. Not celebrated as someone like Ian Banks, but as well crafted and readable.