Necessarily speculative, but here goes...
Let's look at what "the initial concept" really was.
The post-Apollo vision was to build space infrastructure that would enable the manned exploration and exploitation of the solar system. The surface-to-low-Earth-orbit reusable shuttle was but one part of this grand plan, as shown in this 1970 slide from Marshall Space Flight Center.
Notice the many orbital stations around Earth, the Moon, and Mars. Reusable nuclear thermal vehicles. Reusable space tugs. Also the smaller, fully reusable shuttle.
When budget realties and realpolitik got into the process, the fully reusable shuttle was changed to partly reusable, trading development costs for operational costs later down the road. All other elements of the plan were deferred, vastly reducing the number of shuttle launches and really calling the entire rationale for a shuttle into question. Desperate to keep a manned vehicle, NASA resorted to joining with DOD and handwaving the economics of the shuttle.
Would it have been as good as advertised?
A smaller, totally reusable vehicle would have cost less per flight. A much larger fleet flying many more missions would have vastly increased the experience base and perhaps reduced the political impact of accidents. If an F-16 crashes, it makes the news, but it's not a national tragedy, and the Air Force doesn't grind to a halt for years while it's investigated. The shuttles we got were treated as national treasures and their low flight rate and extreme cost made the experience base small and the opportunities to improve them scanty.
You're probably really asking "was 1970s technology up to the task of building a smaller, fully reusable, shuttle that could crank out a high flight rate". Speculative, but my guess is...probably. The shuttle we got was so close to the margins every flight that an enormous amount of inspection, test, and overhaul was required after every mission to make sure it was OK to fly again. It was probably possible to design in extra margin at the cost of performance...but that's largely an economic decision, and a tough one to make if you don't have the grand vision.
Some aspects of your question are covered in answers to these questions:
Technology: How would a state-of-the-art space shuttle be built?
Why did NASA close the space shuttle program?
Why didn't NASA use the shuttle to make a profit?
Why were four Space Shuttle orbiters initially built?
If you have a serious interest in this topic, I highly suggest you read "The Space Shuttle Decision" by Heppenheimer. It's available online here.