a16z's Anish Acharya on the AI era's "permanent underclass" and the reasons he doesn't buy it: "It's a funny dark fantasy that we seem to have as Silicon Valley collectively. Things have never been better, really by almost every measure." "By how distributed all the opportunities are, by the kind of technology we have access to, to the types of ambition we're allowed to have, and to the number of companies independently working on things that are winning." "The last era of tech was a lot…