Let me start with the last thing you said. Is 'the idea is cool' a valid reason to go to Mars? First I think achieving great things is good for humanity - period, but there's even a purely pragmatic motivation as well. After we landed on the Moon the number of people wanting to (and who would) go into sciences, become astronauts, and other such things skyrocketed. The exact same thing is happening in China today where the majority of kids want to become astronauts or teachers. Whereas in America and the UK the plurality want to become streamers, with seemingly the majority having no direction for their life whatsoever. [1] Which next generation do you think will 'win' the 21st century? Even outside of competitive aspects, which generation is going to create a better country?
As for the radiation, you're again primarily referring to space radiation. Table 2 on the study shows their measured Martian surface level radiation level, which is less than the ISS. The space radiation is something that needs to be dealt with. Fortunately the current estimated trip length is 50% of their estimates - around 3 months, space weather events can be more effectively shielded against, and so forth.
And filtering out perchlorates isn't some advanced industrial process. It's literally just filtering water in a normal way. Plain old cartridges (specialized for perchlorates) like you might use in an at-home filter would work just fine. The reason I mentioned astronauts being enthusiastic about going to Mars because you have the most qualified people on Earth enthusiastic about it, some of the richest people on Earth enthusiastic about it, and billions of others. So it's obviously going to happen. There's no coercion or sacrificing people or whatever. It's a free world, and hopefully in the future we can make worlds plural.
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Robots are an interesting topic because people don't seem to understand how limited they are, though it's self evident if you think a bit more deeply about it. The most fundamental problem (among many) is that moving parts break. So for instance Curiosity's drill, as underpowered as it is (able to dig a narrow hole to about 6cm) broke after about a dozen light activations. It took a team of scientists almost 2 years to come up with a work-around that still left it crippled, but at least kind of workable.
And the drill is just one aspect. The more obvious one is moving. You have to be extremely cautious when doing such meaning major human oversight, and with an average round-trip latency to Mars of around 25 minutes, well - you don't move much. On average Curiosity travels about 1 mile per year. Try to imagine digging into the secrets of Earth by using a drill you can use a few times for holes up to 6cm deep, while traveling at mile per year. We're not even scratching the surface of Mars, quite literally.
And this is isn't just a technological problem that can be hand-waved away, because the reason things are in this state is because moving parts break. A human on site could have likely easily fixed the rover's drill in about 30 seconds, or just did a way better job of 'drilling' with a spoon. Humans will discover more about Mars in a week or two than the past 60 years of probes and rovers have, and likely even more than another century of such would achieve.
[1] - https://www.statista.com/chart/28802/childhood-aspirations-i...