Earlier quoted context omitted.
Should have, but didn't. At least not for manned spaceflight. We learned how to keep humans alive in space way back with the Gemini project. A long-duration orbital sojourn could have been had for the cost of the ISS. At the end of the day, I struggle to think of a single big thing we can do post-ISS that we couldn't without.
It may not make headlines, but the knowledge we have gained about long-duration human health in space from ISS is utterly beyond price. For all its problems, that alone makes ISS worth it.
The knowledge was valuable, but not priceless. The same data could have been gathered, many times over, with long-duration multi-member orbital missions. We could have probably gotten an interplanetary flight in, too. The staggering cost of the ISS crowded out a lot of good science.