Medicare may restrict access to controversial, pricey Alzheimer’s drug Aduhelm

Private insurance companies have drug formularies and attempt to limit care to what they consider "medically necessary".

And then drugs are also already heavily regulated by the government.

Up until there are unlimited resources, there will be decisions about how to use resources. Restricting access to something that costs a lot and doesn't seem to have much benefit is not a bad decision in that context.