This kind of issue is another reason why I advocate for four books, BECMI-style one book core, plus the traditional trilogy.
Because it isn't just the dragonborn fuss. It's the dragonborn + gnome + half elf + tiefling + half orc + a bunch of other stuff fuss. And if they stick with the three book model on launch, they are damned if they do, damned if they don't, on
every one of those. And that's just the races.
One of the things a single core book does is allow (require) them to be really picky and traditional on what goes in that core book. But at the same time, they want to quickly follow up with the rest, and a web enhancement ain't gonna get the job down on this at an emotional level. People want their thing in a book, soon. Plus, there is the practical issue of groups where the DM won't allow something not in a main book.
So it's just a lot easier to have a starting set of books where one is, "sorry,
none of that controversial stuff made it, we were pressed for space, and human, elf, dwaf, and halfing were good enough for BECMI." Then the other three are, "but if you want all that stuff, we've got you covered."
It also doesn't hurt that we know it can work, because that is how most of us in the older crowd used the AD&D 1E trilogy when they came out--as supplements to the Basic/Expert "core".
But I do agree that if they make a crippled starter set/book that is not capable of real play by itself, the whole thing will be doomed. Not because that couldn't be made to work, but because the kind of attitude that thinks a crippled starter set/book is a good idea will permeate the whole development--and worse, marketing.