Good to know that expecting tools to use in a game supposedly about unlocking your imagination is regarded as hyperbolic now. Its not as if ready to run content isn't welcomed. It should be supplemental to the foundations of the basic game (which is to make stuff up) instead of replacing it.
Coming at it from a new player's point of view, which do you think is easier to learn:
"Here are 100 different monsters, here are rules on how to create encounters, how difficult those encounters should be, how often you should have them, what all these special abilities do, what kinds of stories you should make up, what makes up an RPG, how player abilities work, and a list of 100 different variations on class/race/class features/spells/equipment. Use this in order to make up a storyline the same way that authors write novels but make sure you follow these rules to get there. Then help your 5 friends make up characters using these rules. They'll have a lot of questions so make sure you understand the rules well so you can answer them. Oh, if you're having difficulty with this process, you can also get some ready to run content."
VS
"Hand these characters to your friends, let them read them until they understand what abilities they have. Then start reading out loud right here and follow the instructions as you go along."
Next I suppose comes the 'you are not the target audience bit'.
You aren't. You've played the game before. You know what an RPG is and you like to customize the game to suit yourself already. You are not just an experienced player, you an an advanced player.
The starter set is not for people who like to make up stuff they think will be fun.
That is precisely correct. The starter set is for those people who have no idea what exactly they are even supposed to make up(or even that they were supposed to make up something in the first place). How do you make up a story about elves when you have no idea if elves are tall or short. You have no idea what elven culture is like. You have no idea even what an elf IS or if they are even supposed to be involved in your story. You don't know if the adventure is supposed to involve fighter orcs, reading books at a library, or playing on a slip and slide in the front yard of someone's house. You're a completely blank slate coming into this hobby in terms of "I've heard this D&D thing is fun...now explain how that works."
To me that's about the same as saying "This Starter Movie Kit" doesn't explain how to properly frame and light shots. Instead it just gives me a list of movies to watch that it thinks I'll find interesting and directs me to a course on directing once I've watched those movies.
There is a spectrum in D&D that ranges in the same way movies do: People who watch movies, people who watch lots of movies, people who watch obscure movies, people who film family events, people who make their own amateur movies in their backyard with their friends, people who make youtube movies that 100 people watch, people who make independent films that get released at Sundance, people who make blockbuster Hollywood movies, people who are critically acclaimed award winning directors or producers.
The amount someone needs to know to watch a movie is completely different than the amount someone needs to know the be an award winning director. Also, the amount someone needs to know about filming is even different between what you need to know to film a party with your friends and filming a movie that will be released commercially.
The Starter Set is aiming at the low end.