Good question - I think it would be hard for me to say, since I'm not at the very beginning of my career (though in startups, aren't we always at the beginning, to some degree?). My point there is just that when I did first start my career, I was working 80 - 100+ hours/week in investment banking, so no, there was no time for writing - or at least I didn't make time for it. And in the little time I had left over at night or on my partial weekends, I would dedicate it to working on/planning for my future startup (primarily the one that failed swiftly after I quit my finance job). I think at the beginning of your career, the highest-ROI activities are the ones that deepen your knowledge base, experience, and expertise in your industry/business/topic of choice. However, writing can be a good reflective activity that actually makes you think more, so if it does help deepen that expertise, perhaps the ROI is there.

Personally, I find writing very therapeutic and probably the least stressful of activities to which I allocate my time, while also being one of the most mentally-stimulating, creative, and thought-provoking. Once you get to a point in any job or activity where you can do a lot of it on auto-pilot (either it no longer scares you or just isn't that difficult anymore), I think it's important to find a new challenge. Writing has been one of those opportunities that has challenged me to think even deeper into the skills I already leverage in my businesses, while also leading me to research others that I may not utilize on a daily basis. For that reason, I actually think writing does force me to deepen my knowledge - and also the fact that the more I write, the more I want to read, which of course helps as well.

I hope that kind of answered your question? It's a hard one, since there's always a trade-off, but I think if you're learning and creating (both of which for me, writing does entail), then it's probably a good use of time. But a great question to ask yourself whenever deciding how to spend your time.