I am saying that doing an 'introductory' game that deliberately denies certain aspects of gameplay, or requires the use of other purchases to be complete is not a product worth making.
I don't understand this statement. Clearly, an introductory game is a success (and therefore worth making) if it is:
A) broadly accessible
B) enjoyable
C) encourages purchasers to seek out more product of this type
There's nothing about these requirements that demands that the introductory version of the game cover EVERY aspect of game play or be entirely self-contained. (Indeed, it would be a fairly poor introductory product if no one who bought it ever felt the need to buy anything else.)
You cannot arbitrarily stipulate which aspects of the game new gamers will like -
It's not arbitrary. The core of the role-playing experience is what happens at the table on game day. That's a very clear and considered dividing line.
and by denying them these aspects, in what may be their only attempt at playing the game, you are reducing you chances of getting them interested in the game.
Who are you afraid we're excluding? The player who doesn't like playing the game, but loves creating characters? The DM who doesn't like running the game, but loves crafting adventures? I'm not convinced that this is a significant or sustainable portion of the market.
For people who love playing the game, but want to create their own characters, there's a book for them to buy. For people who love running the game, and want to create their own adventures, there's a book for them to buy.
For people who REALLY want to start out creating characters or creating their own adventures, they can just skip the "Adventure Box" series entirely and go straight to the core books.
Character generation and world creation are fun parts of the game, not chores that newbies cannot possibly handle.
Sure, but it's an extra level of complexity that prospective role-players have to take care of before they can get to the heart of the gaming experience: actually sitting at a table and playing the game.
That's the point at which they'll determine if they like RPGs or not. If they don't like that experience, your intro product has failed, regardless of what else you provide in it. If they like role-playing, then you can provide them next steps.
The goal is to get a product into the hands of as many customers as possible that will help them answer the question "Will I enjoy tabletop RPGs."
Moreover, if you take them out of the game you're not really getting an authentically 'complete' D&D experience.
The goal of an intro box is not to appeal to some Platonic ideal of what a role-playing game should be. It's to find new gamers.
I mean, it's just common sense: If you have a friend who thinks maybe they MIGHT be interested in playing an RPG, what do you do? You invite them to a session, you give them a character to play for the afternoon, and you let them see if they enjoy it or not. This is that experience, in a box.
(But with an adventure that covers many sessions, and rules for leveling up -- per the original specifications.)