I have to strongly disagree on this point. I constantly see in discussions and people asking about how to DM this notion of "doing it right". I think it's vitally important that players and DM's find their own way to do things rather than being told by others what is the right and the wrong way to do it. Throwing DM's and players in the deep end is, IMO, the most fun part of learning how to play and fosters a more creative and passionate player as they tend to be less tied to rules as laws and more inclined towards rules as guidelines.One thing I definitely agree with the article is the concept of a real DM teaching manual.
I learned DMing when I was 20...and I remembered being terrified that I was going to screw it up! My friend (our groups DM) gave me a sample adventure to run, walked me through the basics, gave me advice. A few sessions...and the rest was history. But without that initial training, I might never have started.
Playing with the generation of players who began with 3.x or Pathfinder is, for me, exhausting. The encouragement in those systems to strictly adhere to RAW has been a major part of why I haven't enjoyed or participated in such games for the last decade. What I'm finding with new players in 5e is a willingness to let their imaginations fly and the result is a far more enjoyable game for everyone. I'd like to see that encouraged and a DM's guide is something that I think will only serve to discourage that type of play.