It is always important to remember that STS is, by and large, 1970s technology.
But I mean, name one other 70 ton + spacecraft, that has flown into space and returned to Earth intact, more than 100 times. Or had the same crew capacity as the shuttle, or acted as an orbital work platform, or allowed the retrieval of payloads from orbit, or allowed in-flight repairs to stricken spacecraft. Or had the ability to launch station modules, that were just components, rather than having to be spacecraft in their own right.
We all know the disadvantages and problems of the shuttle. But it's easy to dismiss that it has any upsides or advantages, or capabilities otherwise unseen in spaceflight. Which it of course does; they do exist, they're just marred by those same problems.
No other spacecraft has yet launched that amount of people into space. And the whole 'story' of a shuttle mission from launch to return really gives one a feeling that humans are competent in space. It is not a three ton, three-person capsule surrounded by disposable infrastructure.
I know everyone is going to shout "Buran", and yes, Buran had some interesting aspects that seemed to be better than those of STS (increased carrying capacity, increased capacity to orbit, more powerful, non-toxic OMS/RCS), but it was unfortunately only tried out once, on an unmanned flight, and almost certainly would have experience many of the problems of STS. Only the US shuttle has really seen action, and shown the attibutes of it's design and engineering in operation.