The Shuttle had a purpose and objective... it was unable to go beyond low earth orbit - by design. Think about this, at the height of the Apollo program the US Congress(the body that determines NASA's budget) allowed NASA 4% of the entire federal budget, which is about 30 billion dollars, nowadays Congress allows NASA one half of 1% of the federal budget, which is 18 billion, that is a lot less resources. So NASA does what it can with the limited resources. There was a similar gap between the end of the Apollo program and when we started using the shuttle too, so no NASA, specifically, is not done exploring space at all. I hope this was informative on some level.