"The leadership was struggling with the vision of the company. It was pulled in many directions - sometimes ad-hoc based on customer feedback or angel advice."
and
"I wanted to have a significant impact so I was constantly asking the founders to work on the long-term vision and culture for the company. I also told them that VCs invested in talent and not the idea."
Being pulled in many directions at once is characteristic of new companies. Furthermore, you yourself were pulling it in one direction (it would appear). So, then, were you also guilty of this ad-hoc influence? I'm not sure what to take from this apart from "my pulling was good, their pulling was bad."
Also,
"The culture was bad. Engineers were constantly told what to do."
I think that this is pretty status-quo (you're an engineer, not an idea guy/founder after all). Not only that, but someone needs to hold the reigns. I couldn't imagine being a founder and not telling engineers what to do. Like the other HN'er, I need some clarification here. Were you being micromanaged? (And even that may not be a bad thing..)
Let me make a small aside about culture while I'm at it. I don't really buy into this "company culture" bullshit. It seems (to me at least) that it's mostly self-gratifying mental masturbation. Instead of being so obsessed with "culture" -- it's mentioned two or three times in the essay -- why not bring up more substantial issues up? After all, maybe it just wasn't a good fit (but that has nothing to do with culture). That would be like a girlfriend breaking up with me because of my "person culture." It's a meaningless platitude that's thrown around far too much in startup circles.