The question isn't whether it's intellectually stimulating or not. The question is whether a minute spent on Hacker News is best spent on Hacker News or better spent on something else.

Is reading about a new Javascript framework on Hacker News more intellectually stimulating than actually writing some code? Even if you're just trying to get your 8-hours-of-butt-in-seat-time in, it's a pretty questionable assertion, IMO, that HN is the best you can do with that time.

I would say in general depending on where you are in your career, knowing about a lot of stuff on a shallow level and knowing one or two things deeply is a competitive advantage. Especially as you move more into architect or consulting roles or even CTO.