I agree with you on the idea of simplicity.
I think/fear they are preparing this as a dial, but its a dial for customizability, not actual mechanical simplicity. So if you want a "Basic" human fighter, he will be there....what you didn't know was that he's actually the same as a Human Fighter with a Soldier Background and Defender(?) theme that the "Expert" player might swap for other Backgrounds or Themes. Of course, whatever Background or Theme you have will be composed of Skills, Traits, and Feats, which the "Advanced" player will be able to swap out as he/she desires. So if there's 20 "stats" to write down in Advanced mode, there are 20 stats to write down in Basic mode, just with less choice about what they are.
I suppose as a simplifying house rule, one could choose to ignore the background skills and say that the DM can give you +2 (or whatever the skill training bonus is) for roleplaying considerations like writing "Veteran of the Goblin Wars" in the Background box. I'm not sure how that would work for the Themes and Feats portion of the game, though. I'm hopeful that 5e feats are much bigger things than previous editions' feats. Thus, they could be more like "class features" and not so much a pile of fiddly bits.
Personally, one of my design goals would be for a 5th level mundane character (no spell lists) to be easily written on one side of a standard notebook sheet. I don't get to pick the design goals, though.