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.