It was canceled because of budget issues and also the fall of the USSR itself. USSR wasn’t really doing too hot at the time, economically. Not because it was dangerous. It was obviously proven space-worthy.

The only boondoggle was not iterating on the design, especially when they couldn’t launch intelligence payloads to polar orbits. They should have kept the original fleet and been given funding to develop another one - a “space car” for the Shuttle’s “space truck” - that could ferry lighter payloads and a smaller crew to more varied orbits.

I used to think like you but I’ve grown to like the Shuttle. Without it things like the final Hubble repair and building the ISS would have been a lot more complicated. Yes, it was a very ambitious design with more fatal flaws than we’ll ever really know about - what if it had had a major issue in orbit - it kept the dream of manned spaceflight alive, and built a ton of experience at NASA for managing manned spaceflight.