The fundamental problem is that moving parts break. This results in things like rovers being exceptionally conservative in both their design and behavior, out of necessity. For instance Curiosity's drill can only drill to about 6cm, and even then it broke after 7 limited activations, which then took a team of scientists 2 years to come up with a partially effective workaround. A guy on the scene could have fixed it a few minutes, or done just as effective 'drilling' himself with a spoon. We're literally not even scratching the surface of what Mars has to offer.
Another issue is in mobility. That involves lots of moving parts. So Curiosity tends to move around at about 0.018 mph (0.03 km/h) meaning at its average speed it'd take about 2.5 days to travel a mile. But of course that's extremely risky since you really need to make sure you don't bump into a pebble or head into a low value area. So you want human feedback on a ~40 minute round trip total latency on a low bandwidth connection - while accounting for normal working hours on Earth. So in practice Curiosity has traveled a total of just a bit more than 1 mile per year. And as might be expected its tires have also, broken. So it's contemporary travel time would be even worse.
Imagine trying to dig into all the secrets of Earth by traveling around at 1 mile per year, and once every few years (on average) being able to drill hopefully up to 6cm. And all of these things btw are bleeding edge relative to the past. The issue of moving parts break is just an unsolvable issue for now and for anytime in the foreseeable future.
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Beyond all of this, manned spaceflight is inspiring, extremely inspiring. Putting a man on the Moon inspired an entire generation to science and achievement. The same will be true with the first man on Mars. NASA tried to tap into this with their helicopter drone on Mars but people just don't really care about rovers, drones, and probes. It'd be nice to live in a world where kids don't aspire to be friggin streamers when they grow up.
So do human bodies, and the extensive life support systems they would depend on in space, which I think was the theme, more than anything, of this particular article.
The only unique think I can personally add here that we're probably a lot more comfortable with high failure rates for machines than even low rates of failure for humans.