To be honest, NASA is bloody brilliant and should never be denounced for their awesomeness, I agree wholeheartedly that Apollo would have never happened without NASA. That said, there are endless projects that could never have happened without them. The amount of science and tech they feedback is incredible.
Now... SLS is a project which has dumped billions into the American economy and has been a major component of helping the US recover from the DotCom Boom and later financial distastes of this century. Companies like Lockheed, Boeing and others provide a great service as money launderers for congress trying to stimulate the economy in different regions. They however are bureaucratic cesspools of filth and decay that fail at 9 out of every 10 projects announced since many of those projects really were intended to do nothing more than just feed money into the economy.
SLS would have never happened if it weren't for private space.
How many failed space projects have there been since the original Space Shuttle?
How many years did we fly the Space Shuttle and perpetuate the life of the Space Shuttle before we finally decided we had to move on and finally make something more?
This is because the ULA guys and Boeing never actually needed to complete a project in order to get more money for not completing it. It is too much work to bid on and negotiate for a new space launch vehicle. So, it's better to drag each one out as long as possible milking the government for more funding. NASA has been crippled by the government contractors. What's more is that Boeing and ULA are just so damn big, there was no other companies that could meet the minimum requirements to bid on these contracts, so NASA couldn't even pack up and go somewhere else.
Enter SpaceX and others.
SpaceX has now consistently delivered on inexpensive flights, advancing technology, even making space interesting again. They are a company that survives on launch contracts and while they take funding and government money, as far as I can tell, in the entire lifetime of the company, they haven't taken even as much as just this one SLS contract.
Does this mean that SpaceX is better than government? Nope... but here's the thing, if ULA or Boeing doesn't deliver on space projects now, the government can ask SpaceX or BlueOrigin (who seems to be working with ULA surprisingly enough). This has changed the entire dynamic of the space program. It meant that the NASA, after over 40 years of what generally has always felt like corruption can actually expect their contractors to deliver.
It is also very likely that Boeing and ULA companies may actually save their reputations and do better in business because private space is forcing them to actually be better than they were. Just imagine what would happen if Musk or Bezos got into commercial passenger aircraft and decided to compete with the 787 for example. Planes would cost a tenth as much and be designed to have lower cost of ownership.
These companies have been cornerstones of American accomplishment but when the politicians found out that they could use these companies to stimulate the economy, they started looking for projects to dump money into no matter what the outcome. It was altruistic, but it established a precedent that said "You don't actually have to build anything, just make jobs". And for nearly 30 years, that's what they did.
The design of the SLS, while FRIGGING AWESOME!!!! is just too expensive and placed absolutely no focus on practicality. My guess is a room of NASA scientists and engineers looking at the design and shaking there heads and thinking "This is what we get for that much money?". The entire rocket is probably heavily based on the idea of "If you want something good, we can go back to the drawing board for 10 years, this one we can deliver now".
I loved and adored the Space Shuttle. As a small child when it was being built, I slept snuggling on a stuffed space shuttle doll. There are so many things that made the Space Shuttle awesome and I am sad to know that the space plane concept is dead for now... maybe for the rest of my life. But, can you honestly tell me that the Space Shuttle program was done well by the government?
The Space Shuttle flew 135 missions from 1981 to 2011 with what seems to be an average cost per launch of about $800 million. Are you telling me that with a budget of approximately $1 trillion USD, they couldn't have redesigned the blast shield so that it wouldn't require each and every tile to be removed and inspected one by one by human eyes for each flight? They couldn't have designed more efficient boosters on more efficient fuels? They couldn't have upgraded the computers to more modern technology? How about the Endeavour built for first launch in 1992? They couldn't have made major technical improvements on the design?
Come on... yes, the government and the crooks at Lockheed, Boeing and others got it done, and damn was the space shuttle awesome, but the technology completely stalled for decades because the government and those crooks were as fast and agile as drunk snails in a salt patch. With Lockheed and Boeing bureaucrats involved, it was a miracle we ever launched the Space Shuttle at all.
SLS is a whole different scale from Falcon 9 Heavy, but in most cases, being able to launch more isn't that important. What's more important is being able to launch more reliably. SLS is not a reusable platform. It is excessively expensive. It is possible to launch dozens of alternative smaller rockets for what just one of these cost. But to be honest, for what that thing cost, I would have much rather seen a new space station capable of hosting in-space assembly and deployment of projects like space only vehicles.