Who said anything about settling? If a person is a neophyte about training/MA/working out is it completely uncharted territory for them. They simply do not know what they do not know and, since the choices are limited in the first place they do what is available to them. Where they go from there is up to them.
When you use the phrase, "better than nothing," that suggests that you think that choice is settling.
I framed it as I did to get the question out of the way. Whether you realize it or not a Lot of what has been said in this thread has skirted around the edges of implying some styles are crap. The fact that you are implying schools goes without saying. There are people who peruse this site who do not have a lot of MA knowledge. I would hate to know I was the person who drove someone away from working out for the wrong reasons, simply because they misunderstood someone's intent.
Oh, I get it now. You're not having discussions. You're serving the public good. That explains a lot.
So, for the record, then, my opinion is that you're going to be much more successful learning a combat sport or taking cardio-kickboxing classes if your goal is self defense. In fact, I think you're probably better off at a parkour school or doing crossfit than training in many styles that are 'self defense' oriented, if your goal is to be safer.
Now, if you equate fighting skill to self defense, unless you're being mugged or assaulted frequently, the best you can do is develop skill in a complimentary skill set. You can get a job as a cop, a bouncer, join the military, or become a freelance mercenary. You could, I guess, join a gang or get yourself arrested so you can do some hard time. I bet those guys have really solid self defense skills. Or, if those aren't on the table, you can get pretty close training MMA, or another combat sport, and developing skill through competition.
I use ninjutsu as an example a lot, because it's the quintessential non-combat, self defense art. But to be clear, if you think it's fun, like the costumes, or are interested in the culture and history of the art, great. Knock yourself out (no pun intended).
But if we're getting to what makes people less likely to be victimized, I believe it's more to do with building real skills and understanding the subsidiary benefits of the activity. It's useful to train in an art where you get to use what you learn. Judo, MMA, wrestling, Shuai Jiao, boxing... they all have an advantage over arts where you don't use what you learn. And that, in itself, is useful, because you will know not just that the techniques work, but that YOU can make the techniques work. So, when it comes to whether someone will be able to perform in an emergency, the school teacher who competes in Judo is much more likely to succeed in using the skills in an emergency than the school teacher who has learned several ways to kill or maim someone with their car keys. This is because the Judoka has applied the skills in a complimentary situation, in the same way that a cop will be able to rely on skills used on the job if he or she is in a self defense situation.
But that's actually not the part that I believe makes me safer. The big thing is the subsidiary benefits of training in anything that has some structural integrity, which can be achieved by doing activities that don't involve fighting or maiming or killing. Confidence, fitness, coordination, positive self image, feeling like you're a part of a group... all of these things help you lead a balanced lifestyle. Not doing drugs or hanging out in bars, starting fights at picnics or otherwise engaging in a high risk lifestyle. These also help.