I don't think the Humans necessarily must, or should, be the baseline by which everything else is calculated. By definition, that means that Humans are not in any fashion distinct.
There should be a hypothetical 'baseline' humanoid to which all PC humanoid races, including Humans, are automatically superior. It has an average of 10.5 in each of its ability scores and gains no racial abilities that are not intrinsic to the humanoid type.
I very much like the idea that Humans are +1 to everything, thus having an average of 11.5 in everything, with the other races averaging 12.5 in two scores and 10.5 in the others. (Growing less and less fond of racial penalties.) This makes Humans theoretically superior-- albeit less focused-- and better capable of mixing diverse class types.
Do we need to distinguish humans by their ability scores? I mean, we have to start somewhere. Why not humans? Humans as a baseline feels more solid than a nebulous non-entity serving as baseline. Giving them an across the board increase feels like unnecessary bloat to me. Dwarves are tougher than humans. Elves are more (intelligent|dexterous) than humans (depending on the camp you side with). Halflings are more resilient of spirit than humans. These are fantasy tropes from various sources. Why change that? There are ways to distinguish humans without resorting to granting them a bonus to every ability score. This, in my opinion, is poor design, regardless of who enjoys it at face value.
Remember: the new system focuses on ability scores. While many scores will seem close to average, at the high end, through optimization, humans will come out on top every single time.
This may be a case of six of one, half a dozen of the other, though. If you have to give one race a bonus in every ability, something just feels off. It's over-complicating, maybe? Just reduce the bonus the other races receive by a point and the same effect is achieved. You still have the human as baseline, but everyone feels better about option one because the human is bolstered all the way around? It's just weird to me on a psychological level.
A case could be made for removing ability modifiers based on race altogether, rather instead rewarding each race, humans included, an ability that reflects the strengths of the race. In a way, this has already been done. Dwarven immunity to poison. Elven immunity to charm and sleep effects. And so on.
I'm probably rambling on and on and I will pay for it tomorrow, but I hope I made a valid point in there somewhere.
