With delta, you will not reach anything close to herd immunity unless you vaccine about >=90% of the population. There is limited data on the relative safety of these new vaccines on <12 year olds.
There's also going to be diminishing returns on vaccinating the last few percent of the population. At some point, the vaccinated outnumber the unvaccinated so much that the large majority of cases, hospitalisations, deaths, and spreading of the virus is happening amongst the vaccinated. Then there's all the people who aren't eligible for vaccination at all, of course...
That's one example of existing mandatory vaccinations and it's for the greater good of everybody. Nobody cares about that.
I think the parent's suggestion to "just force people to get it" is incredibly simplistic and unfeasible considering the current laws and structure of government.