Except that COVID is known to be brain invasive and to affect cognition.
This looks more like refusing to ever entertain the idea that letting COVID rip was a bad idea and lockdowns and vaccinations and masks were justified because you don't like it, than actual scientific rigor.
As far as the vaccine leading to more mild infection goes the impact seems to be unclear. There's been some evidence that disease severity can have an effect on how bad the cognitive issues get. Some studies have suggested that people can end up with greater cognitive impairment if the infection got bad enough to result in hypoxemia/hypoxia, or if they were put on ventilators, or spent longer amounts of time in the ICU, but other research didn't show any link between time in the ICU and the severity of cognitive issues, and others found that people with mild infections might even be more likely to have problems than those with severe cases.
As always, vaccinated or not, the best thing you can do for yourself is avoid getting infected in the first place.
This looks more like refusing to ever entertain the idea that letting COVID rip was a bad idea and lockdowns and vaccinations and masks were justified because you don't like it, than actual scientific rigor.