It's about undescribables. The world is way too big and way too complex to fit into the symbols we choose to represent it.
The opposite extreme of saying the world operates according to scientific theories and can be understand in terms of quantitative analysis is to say that the world and its events are entirely random. However, if the world is entirely random then why is it that we can predict certain events (e.g., lunar eclipses, the time of the next sunrise, etc). Obviously, symbols are good enough to predict the occurrence of events according to sound theoretical constructs. Hence, the world is not indescribable, at least not entirely so.
I think where you have the problem is when we take our sound theories as information as to how the world actually is. I would agree to a point, but the onus of explanation as to why the world is predictable is on the individual who says it is indescribable. The individual who states that the world is describable has provided their evidence that the world is indeed describable by predicting occurrences previously thought not possible (e.g., solar eclipses, comets, etc).
This is usually done by showing the faulty approximations that theories require in order to be used in phenomological applications, but I don't think this is good enough reasoning by the antirealist. Not only must the antirealist show reasons for skepticisms of a theory's failure (e.g., need for approximations, renormalizations, remaining unobservables, etc), ultimately it must explain a theory's successes if we are not actually describing the way the world is at some fundamental level. Leaving it up to good guesses is not an option. For example, if we can explain the rate of rotation of the earth and therefore predict the next sunrise given certain physical equations, then why not accept that this is how the earth and sun actually are in relation to each other? What is missing from our theories that require us to accept the skeptic's plea that we not think we are describing what the skeptic claims is undescribable?
For many of the most routine science (e.g., engineering applications of science) this cannot be readily answered by the skeptic. The attack is usually always on the frontiers of science. Only until such a skeptic would defy common sense do we cease to hear their complaints.
That's not to say that complaining can never be with just cause (e.g., renormalization is a concern if we want to say that this is the way the world is which is why Dirac criticized renormalization as used in quantum theories), however just because we can do it with some justification does not make antirealism justified.
My remark about simple minds is that they tend to confuse the symbols with the things they are supposed to symbolize.
And, if the sunrise is actually at the time that meterologists say it is, then why doubt it? Sometimes you just have to accept the obvious.