You stated that a different game handles it differently by having advice for different levels of DM. I've pointed out that every chapter in the DMG starts with advice for the new DM. What would you do differently? I don't see how it would help or what it would look like to break it up further. Repeatedly stating that there are different sections is kind of meaningless unless you can show how that would apply.No, I didn't say that.
I have explained again and again how it can be handled differently. I've share my opinion about how to improve the information in the DMG. Some of those opinions you've even shared.
I think the starter set and/or essentials kit is a perfectly good place for new players and DMs to begin. However, I think the DMG should be the second step, and as such, can be organized and presented better with that goal in mind.
I also think it's likely better to focus on helping new folks rather than catering to those who don't actually need what it offers.
D&D game concepts are not that hard to grasp. Whether the DMG is the second, third or fifth step if you want to DM is going to vary by individual. Most people play first, or if that's not an option maybe they watch an actual play stream or read some blogs. Perhaps they pick up the free encounter and watch the associated video. Maybe they get a starter set. If you want to understand how to play the game you should probably grab the PHB (you can get the important bits from the free PDF) as well.
But ultimately? You just have to jump in and DM. No amount of text will make someone a proficient DM. If you don't have any option to actually playing with another DM, odds are your group is brand new and you'll figure it out together. Just like people always have.
Honestly though, if you're just going to continue to repeat the same thing there's no value to continued conversation.