Sure, you can’t always be on a group or look for crouds. Neither it is as good idea to use a knife. At least in my country that would be illegal and you risk going to jail even if it was self defense. You even risk being considered like having a weapon just by owning a “kiu” belt which is a strech. But at least with martial arts you can claim that “he fell on the groud” and that you have nothing to do with it. A knife would make that statement way more difficult to believe.

Circunstances change and you need to adapt. But most of the time the most effective self defense is being able to detect risk and avoid it before hand. For example, the possibility that the risk comes from someone known to you. Or that they use drugs or alcohol to incapacitate you. Most risk won’t come from extrangers in an alley. Most come from “predators” who know how to earn our trust first, so is more useful to learn how to detect that kind of “predator”.

I guess my point is, there is not a sigle self defense strategy that would work everytime. I just added an easy one to your list. Looking for support works many times. Some times even hinting at the idea that your family and friends can “retaliate” might work to stop some threats. For example, hinting at the idea that there are friends waiting for you. Os delivering “upseting” news making sure there would be witnesses in case someone is prone to violent outburst.

Fighting back is a last resort because there is a risk of being sued and going to jail. Just that.