If something isn't broken, okay, great, no need to focus on it. But if something is broken, to a problem solver, this is inexcusable. Things that are wrong need to be fixed. So when you see people complaining about things like startup culture or sexism in tech or whatever else, it's because these people see a problem that can be fixed, so they focus their efforts on fixing it. Most people who comment on these types of things aren't just complaining, they're offering solutions or their thoughts on what the "real problem" is.
Personally, I feel the whole "positive attitude" thing is a detriment. People with "positive attitudes" tend to ignore problems because they don't want to upset others or make waves. These problems tend to fester until people like me (problem solvers) get so tired of it we just leave.
If all you want is to be happy, fine, be happy, do your thing, ignore the problems. But if you want to make an impact, if you want to fix things and make them better for yourself and others, you have to focus on the things that are wrong and you have to complain and offer solutions and build solutions and piss people off until things get better. Making things better is always a fight; it's always a struggle; and you're unlikely to be very happy while trying to improve or fix broken things. Some people think it's worth it, others don't.