While I certainly can see your (entirely valid) point here, I must somewhat disagree, at least personally.
For one, they didn't explore all of the CharGen options and you may very well be able to make yourself and your partner far older than the game demo suggested. That's just a 'pointing out a thing' sort of deal, though. My point of disagreeance follows:
As much as I have absolutely loved the living hell out of Bethesda's games ever since I started playing them with Morrowind, I've been somewhat bothered by the fact that my character has no voice, and I mean that more figuratively than literally (though this becomes a literal issue when everyone but you has a VA in more modern games). Sure, I've made 101 different characters and some of them I've grown very attached to, but 99.8% of their personality exists only in my head with little I can do to express it in game in a way that feels like the world actually acknowledges my character's given persona.
I has mostly accepted this as simply a fact of the choice: Create a character that's pure roleplay or use a pre-made protagonist that the world recognizes. I saw no middle ground.
Enter Mass Effect.
Mass Effect proved every single preconception I had in this area wrong. If it is indeed handled correctly and with the utmost of grace and innovation on the developers part, you can have both. I've only played two different characters in Mass Effect, one of each gender, because of there being one VA per each, but I don't feel I've missed out on anything by being limited here.
I've grown far fonder of Jim and Enyo Shepard than I ever was with some of my TES and Fallout characters that I sank 300+ hours into apiece, and the reason is simply because their array of pre-voiced responses permitted my character to have an actual two-way conversation with another character. Yes, I know this method takes a bit of your own control away to an extent (you can't play a mute, alter the accent or pitch, etc) but something about this setup made these two characters able to feel far more substantial than many of 100% my own devising.
This will of course be up to preference, and I totally get that FO4 is an open world RPG where as Mass Effect is a 3rd Person Shooter with RPG elements. To me, though, I'm looking forward to it. Assuming the voice actor & actress play their roles well and the dev team have given them good lines and a plentiful amount of them per encounter, I think it'll be great. I fear I may have rambled a bit, but I hope my intended point was clear enough to understand.
Now, the issue of the Player Character in mods, however.. well, that's another argument entirely, and one which a voiced PC makes a bit.. trying.