You've hit the nail on the head here. Investing in robots is an infinitely smarter -- and more cost-effective -- play than just sending humans to Mars and hoping for the best, centuries worth of radiation be damned.
If robots really are too fragile to do so much as dig holes in the Martian surface, then lets improve the robots. This has the added benefit of having actual, immediate utility here on Earth!
You're saying that robots are too fragile to rely on for Mars exploration. You know what else is fragile? A human being. And it's far easier to make a robot more durable.
This conversation has helped me understand what I personally believe to be a fallacy behind almost all arguments for the human exploration (much less settlement) of Mars: the fallacy of urgency. There is absolutely no reason why we must drastically increase our exploration of the surface of Mars right now. (or in 10+ years or whenever we would hypothetically land humans there)
If it takes longer than those "10 years" to design more competent and durable robots, who cares? There's exactly zero rush to send humans to Mars -- except that, you know, it would be kinda cool if we did. The money spent on robot research would more than pay for itself in utility on Earth in a way that money spent on shielding humans and sending the cargo necessary to keep them alive in a distant, hostile environment never will.