If the choices are between both a basic and advanced game that are compatible with each other, and only an advanced game, why not have both? Best of both worlds and the existence of the former need not take away from the latter in any way, shape or form.
I don't think anyone here would say there shouldn't be a basic component to the game. Mearls and company have stated that their hope was to make the game have a design possibility that apes BECMI as well as all the later editions... and I don't think anyone has taken them to task for that.
But the real issue here is:
How is the game presented to all of us? Both the basic and the advanced versions?
Whenever we see posts by folks who say that the Player's Handbook should present the basic "core" game (in order to make it easy to understand)... what seems to be what they are saying is that's ALL that would be presented (at least in the beginning of the Player's Handbook). The "basic" version of the game. You open up the Player's Handbook, and those first couple chapters on description and character creation would ONLY give you the aped BECMI rules. And that anything "complex" on top of that... things like Backgrounds, Specialties/Feats, Fighter Maneuvers, the non-four base classes, etc. etc. etc... would not actually appear until the "modules" start showing up (either in later chapters of the PH, or even in entirely different books.)
And that's where many of us are saying "Hold on."
I do not believe you need to have to completely strip out all the "complex modules" (if you'd even call Backgrounds "complex", although some people do) out of the opening chapters of the first Player's Handbook, and it'd be really silly if you did. You can present all the character creation guidelines in those first few chapters (basic and complex, modules and non) and just tell people (via sidebars and the like) how to play the game "basic" or "advanced" or anything in between by pulling those bits you want out of the group that gets given.
Yes... it
would mean that someone who wanted to play just the basic core game would have to
skip over the information on things like skills and feats within those first couple chapters of the PH in order to get to the core... but that is a much better
organizational option than splitting all the information into two different sections, just so that the basic core gets separated from all the additional options you could add to it. Because quite frankly... the number of people who will want to play just the core without ANY options or modules is an exceedingly small percentage of the player pool I believe. At the very least... most players will want to use the extra "non-core" classes, races, and probably Backgrounds/skills. So making those folks flip to the back chapters of the book (or buy another book entirely) is doing no one any favors.
Now this being said... I also have always thought and said the game really should get released in two versions... the hardcover three-book model that covers the entire game (like usual) as well as the boxed set beginner's game. And with that one... yes, absolutely I think it'd be completely fine should that beginner's game include only the basic core-- the four base classes, the four base races, no Backgrounds, no Specialties, no Fighter Maneuvers except for Deadly Strike, no alternative casting mechanics, no Specialty Spells, condensed spell lists, and so on. That could be the place to have your base game. One specifically designed, laid out, and published in that format for those who want it.
But please don't demand the actual hardcover Player's Handbook use that format too.