If anyone is at risk of being hospitalized if they catch it, they should absolutely take the shots. I would encourage them to do everything you can to stay away from people, wear your mask, get all the shots you can get, cover yourself in hand sanitizer if you want to. Protect yourself. Being 100% protected from the virus is entirely a personal responsibility. At this point, if you do everything necessary to protect yourself there is NOTHING anyone else can do to give you Covid. You do not need non-vaccinated people to protect you, you can and should protect yourself if you feel you need to be protected.
I exercise, take vitamins and have built a healthy immune system and that's why when I caught Covid it was incredibly mild. Some people just have weak immune systems. Other people choose to sit their obese butts on the couch, eat Doritos, pop pills, and take shots to try and stay "healthy". Different strokes for different folks.
Your reasoning for why you got only a mild case of covid is only partially correct.
I agree that a good immune system is important. I never take the flu shots and I have never gotten flu.
However, the amount of covid particles that get into your system play a far more important role in the severity of the illness.
If you "inhale" a small number of particles, your immune system will probably kick in and prevent serious illness.
If you "inhale" a large number of particles, your immune system will be overwhelmed before it can produce enough antibodies.
That is the reason for getting a shot. It teaches your body about the virus and your body can react much more quickly.
In the early stages of the pandemic, many people in nursing homes died from covid. Being elderly, their immune systems were probably not as good as when they were younger. But, people living in nursing homes are in constant contact with one another and live in comparatively confined areas. They infected and reinfected each other.
Being at a football game on a windy day is a lot safer than being in a poorly ventilated office building or bar or restaurant or church.