How?
Is the internet a net positive or net negative thing? How about Social Media? Is it maybe even more complex such that we can't tally up positive/negative "points" and a term like "net positive" doesn't even make sense for these things?
Here's a bit of an oversimplification: - is what you made useful to anyone? If it's not, no one will use it so it doesn't matter. - does what you made help people be more productive or less productive? - does it help improve people's health or degrade it? - does it give people what they want in the short term at the cost of harming them in the long term? - does it help some people while actively harming others? - does it help people but harm the environment or other creatures?
Etc.
Most failure comes from not getting past the first question. These are easy questions to ask but very hard to answer. Most startup founders make up answers and then go nowhere and waste a bunch of time/money. Even smart people doing their best fall into this trap. Our system isn't good at developing people to be good at empathizing at scale. When people try to empathize at scale they over-generalize to the point of near meaninglessness.