Worse, neither the writers nor Spiner appeared to have any idea why Data wanted to be more like humans.
Dude, it's Star Trek. One of the major themes throughout (including the TNG pilot, where Data is introduced) is
answering that very question: how humanity (or at least the version of it normally depicted there) is something to aspire to. Why would Data/Spiner himself need to spell it out for us?
well to be fair, Spock didn't aspire to be human. He preferred the Vulcan path.