I believe that the risk of myocarditis in young men was increased after second dose so we can't assume that each vaccination is discrete as this totally ignores interaction with the effect on innate immune system. The innate immune system is poorly understood.
This is not just about the Covid vaccination. My mother developed severe and crippling life long rheumatoid arthritis after the flu jab. It is a known side effect. Autoimmune conditions can manifest after this sort of vaccination.
On a population level it is beneficial (especially for those with high risk) but on a personal level it is a roll of the dice. If you are not at high risk the cost/benefit may not be worth the risk. This is the information we need to make an informed decision.
But in the absence of understanding of individual immune status, or understanding of how vaccination interacts with innate immunity (2 years in) with a virus (currently) with low risk of severe morbidity or mortality for those under 75, rationally, why?