Yes, isolation can certainly reduce your immune system’s readiness, but unless the child was completely isolated from a very young age, I doubt it would ruin it entirely. I suspect something else is going on here.
Absolutely. One or two years of school lockdowns, when they are leaving home routinely for other activities, isn’t weakening their immune systems. That’s pretty much the same as home schooled kids and they don’t have a history of compromised immune systems. It’s the vaxx. Lots of medical experts were predicting this very result a year and a half ago.