Not dumb at all
Whatever redundancies and safety features the Shuttle has, the bottom line is that unlike any manned vehicle I can think of that launches on an expendable, there is no real escape system.
There are oddments like the sliding wires, and many abort options for benign failures, but in a "Challenger"-like incident, you're pretty much boned.
The capsule designs I've worked on for contracts all have robust abort systems, but admittedly, the design problem is a hell of a lot easier for a capsule than for a giant orbiter.