I've often wondered similar things. While science is still being done and many people are arguing that, the level of accomplishments haven't yielded nearly the same results for the average individual compared to what happened in the last century or further. I blame this on society and mainly on capitalism, which only looks to fuel profitable endeavors and people are only looking for the cheapest means to stay alive, or how to make the most money in life.
Space, deep sea, nuclear... general exploration and development as a country has ground to a halt. Instead we're focusing on wars in countries we have no reason of fighting for and patents... then exploiting them. Our country may not be dying, but it's march forward has definitely slowed down. Everyone is out to make as much money as possible. Exploration and being adventurous is no longer part of American lifestyle. It's all about being safe and living as long as humanely possible.
No one takes big risks anymore, it's all about small calculated decisions (mainly decided by a machine), which we bet on which will show income. Even the space industry has somehow ended up in the hands of the private sector, which may seem great, but wont work in our favor down the line when everyone depends on them for their services and the government can't take over because that would be unAmerican.
Our country is totally mismanaged. Our society is bombarded constantly by capitalist propaganda (buy this and you'll be happy, take this and you'll be healthy) and shows designed to placate the mind. Our education system is starting to break down as the less intelligent take over and see fit to destroy something because it doesn't provide instant, easily quantifiable results.
Capitalism may have founded this country, but we've gotten to a point where we've outgrown it. Perhaps not completely... but we have to a point where it's started to hinder development outside of how to shake the most pennies out of the average citizen. This is a time when we actually need a leader to step up and push big businesses out of the picture and actually plot a direction for the country. Sadly, we haven't seen a president like that in many years... or a country that's willing to accept him.