I strongly agree with all of this. I made the same decisions that you did, and while it worked out well (we rolled between 90 and 95 on https://danluu.com/startup-tradeoffs/), it was clearly a negative EV play. I wouldn't have done it if I didn't have a solid record at an established company (so that I could easily return to a similar job at any point), or if the income reduction would have had a material impact (which basically implies no kids and no plans to have any in the next few years, no mortgage or student loans, and no health issues).

I kind of feel that to a first approximation, recommending against being an employee at a start up is the right advice.

Absolutely.