i wouldn't describe the aca as a one-size fits all but it does create a minimum set of benefits that all plans in the individual and small employer market must cover (note: nearly all large employer plans already cover these benefits). previously most plans in the individual market did not offer very comprehensive coverage and had a number of exclusions (e. g. maternity mental health coverage even cancer treatments). the idea behind insurance is that it is spreading risk across a large group of people. at any point in time many people will be healthy and won't need to go to the doctor.
why is the aca a one size fits all policy? why do we have to pay for health services that don't pertain to us?