So you agree that there are no shortcuts? Some athleticism and strength is needed, but, a lifetime of technique and training compensates for the relative strengths of attacker and defender?
I agree there are no shortcuts to be a martial artist.
If someone says they will make you a martial arts master in a week or a month or a year they are not telling the truth, it is all sales and they are best avoided. However you can take a self-dense class, if it is done properly and be given some tools to use. But without training those tools are useless.
You can also train 30 years and be considered a Shaolin Long Fist master but if all you have ever done is forms and applications in controlled environments and you have never really been hit you may find all you have learned is useless after the first time someone really hits you.
Also Yang Chengfu at near the end of his life was close to 300 pounds but I would not want to have been on the receiving end if I was an attacker. And there are Videos of some rather tough old Bagua masters that are far from svelte you couldn’t have paid me to go up against.
You can learn techniques to get away such as eye gouges, step on the knee or instep. throat strikes, etc that can help if one trains them but go to one or two classes get shown one or to times and never do them again... chances are if an real attack occurs those will be useless.
Much of it is all training to make things automatic. I know of a woman that trained Sanshou for many years that when attacked did what came naturally, punched her attacker right in the face. He got up and tried again and she punched him in the face again he got up and ran away. But it was automatic no thought just punch and that type of response does not come from one or two classes.
But the best defense, if possible, run.