It's not about "learning to not do that single thing" but learning from everything you picked up during that period, good or bad. And even if what you did had the net-effect of being negative to society, you can learn from the things you experienced during that time, meaning it wouldn't be a waste, at least in my mind.

> I don't think I've ever spent a lot of time and effort on an activity that broadly harms society

Me neither. I worked in the cryptocurrency industry, sold drugs, interacted with gangs, and a bunch of other stuff but none of them broadly harmed society, so seems we're more or less the same on that point.

But everyone's frame of reference and reality is difference, there is no absolute truth here, trying to paint it as such is actively doing a disservice to any sort of discourse we could have about the subject.

One could surely argue that making "paid browser extensions" somehow have a net negative impact on the world, and if that was proven, would that mean all the time you spent on those sort of projects were suddenly wasteful and you should have realized this up front? Seems inhumane if so.