Do you regret doing your PhD in math? Reason I ask is that I thought about going to grad school for math but decided against it. It just seemed like it would be postponing the inevitable of finding a job that had little to do with my "passion". I definitely see the appeal of doing a PhD in a field with better industry employment prospects (e.g. AI in CS if you're into that), but less so for fields like pure math that aren't as employable outside of academia. I'm curious if you felt the experience was worth it, though

I did a PhD in math and if I were to do things again, I'd do applied math because I think I enjoy applied math at least as much as pure math (this is not true of everyone) while also having it have more obvious job prospects. I did pure math in part because I was told it was easier to go pure->applied than applied->pure. I still think that is true and was a not an unreasonable way to choose what to study. I fundamentally had a very good time in my PhD (I would absolutely describe it as fun, though that would only be part of the picture) and learned a ton and now am transitioning to applied math in exactly the manner that I had been told would be possible (though I feel like I did this more by luck than by it being systematically possible).

I wouldn't say I regret it, but that almost doesn't feel like an applicable word; it felt inevitable to me, so it's hard to imagine any other path. Like, at the end of undergrad, all I wanted to do was think about math all day, every day, and that's what I got to do for the next five years. There was no convincing 22-year-old me to do anything else. Only near the end did the novelty really start to wear off.

N.b. I'm in a very lucky position career-wise now. If that were not the case, maybe I would feel more regret.

Perhaps you would have gotten your thought across more effectively had you said something like "more fun in my opinion".

I tried a PhD in ECE before dropping out with an MS, and the last word I would use to describe my experience is "fun".

Yeah, fair enough. It's more like it could be more fun, if you're obsessed with the field, and your advisor isn't terrible, and your program doesn't encourage cutthroat competition (by e.g. admitting more students than the faculty can realistically support), and you're willing and able to live a Spartan lifestyle (in particular, no financial dependents), and ...

I'm lucky in a lot of ways and I sometimes forget that.

I think your previous answer using the word "fun" was spot-on. I have a non-CS PhD that's not really related to what I do today. I would describe what I did previously as "fun"; despite the intensity and worse WLB than life in a big-tech company, you're ostensibly choosing projects that you and your adviser consider fun. In bigtech, you have a lot less freedom to choose what to do. Seriously, if you don't consider your PhD fun, you should just drop out now; if you plan on just going to industry later to make money (esp as a SWE), there's no reason to get a PhD.

It’s interesting, of course, that a similar set of caveats apply to working for early-stage startups - not that this forum would attack anyone for calling working for one fun.