This is quite literally already explained in the review but I'll repeat it here. I used Andreessen's essay as a microcosm for the problem with Abundance: at the level of fuzzy, non-specific exhortations to "build," everyone can agree. Once you get into specifics, that's where the brass tacks are. In Andreessen's case, it means building is fine unless it's near his house. In Klein and Thompson's case, it's not even clear what they're proposing much of the time.