And I, as stated, think this is exactly the wrong thing to do--at least, the way you've phrased it, e.g. limiting people to the Core Four races and classes (human/elf/dwarf/halfling; fighter/wizard/cleric/thief). It enculturates players to think that there is a special or privileged subset of concepts--it perpetuates the idea that some races and classes are The Norm and other races/classes are, even *should be,* limited/rare/weird in all worlds. That's not the spirit of D&D even back in the olden days, when Gygax was perfectly comfortable allowing people to play balors as long as they were open to starting low and aiming high.
And now I'm just really confused, because this paragraph sounds nothing like your opening sentence. The opening sentence reads very distinctly, to me, as "new players should only be allowed to do Very Traditional Things." The rest of the paragraph, on the other hand, is exactly the opposite of that. That is, it reads to me as: don't tell a brand-new player "no" unless you really, really have to because it stifles creativity, and that is the absolute last thing an introductory D&D game should do.
So...I guess we agree? Even though your opening sentence is something I vehemently disagree with? I'm confused.