At the same time, the capital needed to write is virtually nothing. All it takes is time. Editing, proofreading, and cover design are legitimate, important costs, too, but even those aren't that huge. And they only come into play once the book is written, which means most won't reach that threshold.
I, of course, want great writers to be able to devote all of their time to that and not have to work a day job. But I think having to write your first book or two in your "spare" time is an acceptable way to separating the wheat from the chaff.
In other words, write a book or two in your free time. The money you get from those will be your risk capital for your next work.
It's very simple - if there's less money available for a first book, less people will do it. This means that there will almost certainly be less authors, therefore almost certainly less great authors (though it's probably not linear).
Not to say you're wrong, just that talking about "I think it's sufficient" masks the fact that it doesn't matter what you think, there will in effect be less great books written.