Your argument is fallacious because it rests on overstretching the software/hardware analogy. Human brain contains highly reconfigurable hardware, and if some particular computations are practiced enough, the brain will eventually start synthesizing specialized circuits for them, thus dramatically boosting their speed and accuracy. Or to say it the traditional way, practice makes perfect.
Whether it's throwing darts, programming computers, speaking a foreign language, or various social interactions, if you're lacking any experience, your first attempts will be very clumsy, as your general cognitive circuits struggle ineptly to do the necessary computations. After enough practice, though, specialized hardware gradually takes over and things start going much more smoothly; you just do what it takes without much conscious thinking. You may never match someone with greater natural talent or who has much more accumulated practice initially, but the improvements can certainly be dramatic. (And even before that, you might be surprised how well some simple heuristics work.)
"Practice makes perfect" has a rather different emphasis from Roko's suggestion of "running social interactions in software", which is what I was addressing.
But to answer your point, I agree that improvements in social skills from practice can be dramatic, but probably not for everyone, just like not everyone can learn how to program computers. It would be interesting to see some empirical data on how much improvement can be expected, and what the distribution of outcomes is, so people can make more informed choices about how much effort to put into practicing social skills.
I'm also curious what the "simple heuristics" that you mention are.
Followup to: Do you have High-Functioning Asperger's Syndrome?
LW reader Madbadger uses the metaphor of a GPU and a CPU in a desktop system to think about people with Asperger's Syndrome: general intelligence is like a CPU, being universal but only mediocre at any particular task, whereas the "social coprocessor" brainware in a Neurotypical brain is like a GPU: highly specialized but great at what it does. Neurotypical people are like computers with measly Pentium IV processors, but expensive Radeon HD 4890 GPUs. A High-functioning AS person is an Intel Core i7 Extreme Edition - with on-board graphics!
This analogy also covers the spectrum view of social/empathic abilities, you can think about having a weaker social coprocessor than average if you have some of the tendencies of AS but not others. You can even think of your score on the AQ Test as being like the Tom's Hardware Rating of your Coprocessor. (Lower numbers are better!).
If you lack that powerful social coprocessor, what can you do? Well, you'll have to run your social interactions "in software", i.e. explicitly reason through the complex human social game that most people play without ever really understanding. There are several tricks that a High-functioning AS person can use in this situation: