I think that's harsh, but they were built to a price to do a specific job. Where things have gone wrong is that they're now expected to do a more intensive job just at the time they're getting long in the tooth.
And that's the point. They were built to be cheap, and passenger comfort was not really a priority in their design. The logic behind this being that Metro was imagined as a short-hop rapid service, when in actual fact a substantial number of it's passengers use the system more like an S-Bahn type system.
They're draughty, noisy, become like a sweat-box in damp conditions, and due to a combination of the hunting-oscillation that is common on units of this design and an oddly high tendency for developing severe wheel flats offer an exceptionally poor ride.
Metro was converted from a suburban network, and while you can put a different type of rolling stock on a service, it doesn't automatically change it's usage patterns. Indeed we saw this when the bus deregulation exercise took place in the late '80s, and many of the short hop journeys turned out to be forced rather than organic.
This is something Nexus has the potential to get massively wrong with the new fleet too - there has been talk of switching to an all-linear seating layout to create more standing space on the trains in an effort to resolve capacity constraints.
If we see seating removed from trains to do this, and passenger comfort drops further, it will become even easier for bus companies to pick off passengers who will be easily enticed by facilities they can provide much more cheaply, which will further compound the budget crisis.
As an example, I commute by Metro for about 20 minutes each way at present. Due to traveling outside of the peaks I normally just about manage to get a seat and not be too packed in. If the number of seats reduces and I find myself standing for the majority of these journeys, I'll be switching to the bus that goes past the end of my road. Journey time will take longer, but there are more seats, the vehicles are better kept, and the journey is cheaper too!