CJ: I like your question, "Do we write for every idiot that wants to read our books...Or do we write to delight those readers that want to put in a little more effort..." I write for readers who can appreciate my writing. If I wanted to write for the idiots, I'd probably want to co-author a book with James Patterson. Your story about the art instructor reminds me of a friend of mine who was in the College of Creative Studies at UCSB. She was told that her writing was lacking because it lacked sex scenes. She replied, "but I'm writing for kids." This to no avail. So her Parthian shot was a story where the protagonist, on the first page, said, "I undulated my voluptuous eleven year old body." She switched to English as a major.
And all I'm saying to beta readers is that I appreciate them, even when they miss something--as I deliberately make some things to be missed, and this shows success. And I came on to respond to one reviewer who, although I disagree with many of his opinions about when to put in details and when not to, had other valuable insights.
And beta readers can spot things that you don't. Kathy Reichs once had Tempe take off her clothes, plop into bed. She woke up, realized something was wrong, padded down the hall, saw what was amiss and called her colleagues who arrived forthwith. Were all male, and probably delighted. Did you notice that there was no mention of her putting her clothes on? Kathy Reichs didn't. I made the same error with Heather, a (male of course) reader noticed it. It's now fixed.
The nice thing about beta readers is that it reminds me of Fritz Leiber who, before he was a famous published author, corresponded with another would be fantasy writer. They would exchange stories, and ended up writing for the other. Leiber would go, "Wait until you see what Fafred did this time," or "What do you think of the Gray Mouser's new girlfriend?" It's nice to have interaction with readers.