I agree with the principle here, Jon — “pick your brain” is a vague and easily annoying ask, with nothing really offered in return besides a latte.
However, I disagree with the idea that asking to “pick someone’s brain” is the wrong way of going about it.
I have experienced a lot of success and acceptance from people when I’ve asked to “pick their brain” for an informational interview in the past several years. Perhaps it was the context of my email — I made it very customized and followed a similar template as George Weasley’s. I’m sure there are a lot of folks who see the phrase “pick your brain” and cringe, but in my experience, this way of asking has been effective in many cases for me.