Q: What's the difference between ignorance and apathy?
A: I don't know and I don't care.
Idk, to me, stupidity and evil are the two biggest causes of problems and suffering in society, but dumbness/stupidity is actually relative. To a hamster, humans are super smart. To someone of above-average intelligence like you and me, most humans are dumb. And, of course, probably most humans of average intelligence think most other humans are dumber than them...
As for carelessness, people don't seem particularly careless to me, by and large, but I suppose more carefulness wouldn't hurt in a lot of cases. But if you consider disregard for others to be carelessness, then yeah, carelessness is a big problem.