I definitely think that HN has improved me as a software developer, if only to show me how much unknown stuff there is out there.
Reddit is a bit more questionable but I've definitely found useful things in some sub-reddits.
And sometimes all I want is something that will easily wile away a few minutes.
The answer is quite often “not very”.
First, I am far from being above using HN and Reddit, as evidenced by me typing this. So, this is not a “you should stop using X” rant, because I can’t stop using it either.
I think as a means of getting professional news, HN and Lobste.rs are basically unparalleled. These have been an unambiguous success for me
As a means for being informed in general it seems to work, but I’m dubious about the utility of being “informed” about things in which I have no stake or power to change things. Recent example is discussions about Swedish cashlessness. I don’t live in Sweden, nor will I travel there soon. So what utility does taking up some of my precious attention with this un-actionable information have? I genuinely don’t know, but I fear that the opportunity cost of such reading might be catching me in some subtle way.
As a means of entertainment, my original comment stands.
When you do new things in the real world, these become major events that anchor your memories and sense of time. You can probably vividly remember some vacations, concerts, your first kiss, and a thousand other novel life experiences very vividly. But while Reddit feels novel in the moment, in the rear view mirror it is just a featureless void of “Reddit was here”, with no strong memories left to justify the time spent.