Art can be boring and hard to understand. In the hands of this critic, who is known for his monthly Spike Art Magazine column, it is neither. Skewering nostalgia and reviewing the year 2020 are examples of things Dean Kissick does in “The Downward Spiral.” This year, he also branched out, organizing the gallery show “The Painter’s New Tools,” which itself spawned a disproportionate amount of art criticism.