It’s sad that these people know this and still work on them. I can’t imagine living my life day-in, day-out knowingly making other people’s lives worse.
You can work on a bad thing to try to make it less bad, you not being there would make peoples lives worse since the app would still exist but be even worse.
Name any industry and there’s probably some negative aspect to it. Everything sufficiently effective at anything has a high potential for misuse.
They aren't _people_, they are just Daily Active Users. (/s)