We already have solutions to all of those problems. People just don't want to put them into practice because nuclear power is so dangerous it causes like 0.05% of the deaths of traditional energy sources and eating mostly vegetarian diets is just unbearable, etc. What they want are solutions that are indistinguishable from what we have now but still somehow solve the problem. I don't think Mars is going to offer us a free lunch.
As the old saying dictates Mars certainly isn't a free lunch. However, I wouldn't necessarily agree that we have solutions to the problems I mentioned. I'd agree that we have some potential solutions most of which are in very early stages and often quite expensive. Both issues have kept wider adoption from occurring.
Vegetarian diets are neither a new thing nor wildly expensive. They're old as dirt and can be far more economical than heavily meat-based diets. People don't want to adopt them just because they prefer the diets they have now.
