Taste it. If the tannins aren't a problem, it's beer! Boil some black tea for 5 minutes, if you don't know what astringent tastes like.
Boiling grains is generally a bad idea, but decoctions are all about boiling the grains. So, it has its place.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk