I think the problem with the shuttle was it cut corners. The original design was for liquid boosters in place of the SRBs (the cause of the Challenger loss, and probably contributed to the foam problem in the Columbia loss).
In the initial design, I think they also considered air launch, but didn't want to spend money on an ultra huge launcher aircraft, because the requirement was to lift very large payloads.
The "shuttle" should have been merely for human and modest resupply launches and designed for very quick turn arounds. Plus occasional of the Saturn V for unmanned large payloads like space stations and such to satisfy that requirement.
Heck, Saturn V was even decent for manned loads. Not an engineer, don't know how much Saturn V could be improved if we dropped the manned requirement.
And whatever happened to magnestic acceleration? We got to over 1000G without accelerating fuel, back around 1980. It wouldn't have to reach orbit - there are some very interesting hybrid designs.