One big flaw in your argument is that the payload was delivered safely and successfully. They're making great strides towards making components reusable when they never really were before. That they're not perfect right out of the gate isn't reason to give up hope it ever could be.
Actually...the payload was put on the wrong trajectory, so OP's argument still stands.
"Elon Musk’s cherry red Tesla sports car and its dummy test pilot Starman were on a new course hurtling towards the asteroid belt on Wednesday after overshooting their planned trajectory."
The mission was not intended to get the Tesla to Mars. It was to get it into an orbit that showed that they could get it to Mars. Getting it to Mars itself would have required more careful scheduling of the mission, and would have run the risk of needlessly polluting the planet with debris and earth bacteria. The actual results however showed they could get a mass that size into a heliocentric orbit with Mars.
If Earth and Mars were in the right places then with the right payload they could have gotten to Mars itself.
That is bad reporting. SpaceX always planned to burn the 2nd stage until it ran out of fuel.
Elon always said they weren't sure exactly what the final trajectory was, just that the roadster would be sent out as far as possible.
They weren't sure how much O2 would boil off during the 6-hour coast after launch before it departed orbit. That was part of the test.
Also, they weren't heading towards mars - just outwards towards mars orbit. When the roadster crosses mars orbit mars itself will not be nearby. If they wanted to actually reach mars they would have had to launch during a specific launch window when earth and mars lined up at the correct angle. This happens once every couple of years.
That's not at all a mistake. Any sort of overshoot is extremely unlikely to occur with these situations. The public plan was to put it into an orbit around the sun with the perihelion near Earth's orbit and its aphelion near Mars's. Using the additional remaining fuel, they decided to burn until the aphelion reached well past mars towards the asteroid belt.
Guardian is wrong to use "overshoot" as though it was a mistake - it was a burn to exhaustion, the exact limits of which was unknown beforehand (because it was unknown how well the fuel in the second stage would survive the time in higher orbit. Kerosene starts turning to sludge in cryo). Mars-orbit-distance was the lower end of what was expected.
