> Twitter gets extremely mixed reviews from people who are the targets of abuse
That's (as you note) putting it very lightly. It's basically unusable as a public platform if you're moderately famous. Go watch Jimmie Kimmel's bit with celebrities reading mean tweets on youtube and imagine being on the receiving end of it. The ability to lock down your account misses the point, though it does say that Twitter thinks abuse might possibly be a problem (as does comments by its CEO).
Screening out abusive users is a hard problem that hasn't been properly solved yet, anywhere in the world. An eternal September, to revive the phrase. G+/Youtube and Facebook's real name policy hasn't managed to solve it, and Facebook is only able to screen out the worst - gore and pornography, with devolving political discussions leading to many unfriendings this election season. Maybe not quite abuse, but still unpleasant.
If fighting abuse is your life's mission, then join Twitter. See what they're doing about abuse, talk to people who have tried to fight abuse for years, find out what's succeeded, what's failed. There may be some Twitter org-specific implementation barriers, but that's still a learning experience for the future. If you find some Twitter org-specific barriers that are insurmountable, get out.
My bias, here, isn't that I work for Twitter (I don't) but I doubt Twitter's inability to quash abuse has anything to do with corporate governance (other than an inability to spend infinite amounts of money on an infinite amount of moderators).
Humans are still currently the best at understanding humans, and we still do a terrible job sometimes. Computers aren't able to parse sarcasm, idioms, or subtlety, and being fed in plain text instead of speech makes it even harder as there's no vocal tone to analyze either. Twitter's 140 character limit hurts quite a bit here.
I agree that making a difference is key, but the problem itself also has to be considered - the early teething pains at Twitter in reaching "webscale" have been fixed by now (when was the last time you saw the fail whale?), but "people can be assholes to each other" is probably the oldest problem in the world.