Except that we've seen dozens of shuttle from various movies, and 5 series, and we had yet to see a dirt shuttle like this. There's thinking outside the known box, and then there's making stuff up to suit your own opinion.
The "known" Star Trek universe has set a pretty standard precedent for having clean equipment. Again, dozens of ships and shuttle of various series taking place in many different time periods.
My uncle served on a Canadian ship carrying Sea Kings (

) and they are very clean as per they’re routine servicing.
Now we're talking about a prosperous future with fantastic technologies. Is it so un-realistic to have the shuttle service crew keep a little shuttle clean?
ON the other hand, with regards to the picture. We have no context for what or who is using the shuttle in the picture. It could be lost and have gone through a tonne of crap. They are a long way from their home and cleaning is the last thing on the priority list.
That however does not negate my argument that Starfleet keeps their ships in regular service, clean! To think that they don't have the ability to clean with ease in the future is, well, it's just

!