The author of the article is Kim Stanley Robinson, whose Mars Trilogy and novel 2312 include all of the possible in-solar system alternatives you mention and more.
And? Because he wrote several science fiction books on the colonization of the solar system, his word is law on what we can and can't achieve in space?
To be fair, you'd have to make an argument. Like KSR does, with facts and such. Simple Pollyanna optimism isn't an argument.
I hope its such as the optimists predict - a great bright future for us all. Still it's worrisome that each time somebody researches it, they get depressed and won't talk about it any more. Or writes a depressing book.