That's exactly what the Southern slave-holding states said prior to the Civil War. It became necessary not to accept the immorality of slavery. The same is true for marriage and other individual rights. We can't leave them up to the states.
There are just certain policies that work better when we apply them to the country as a whole. We have a
Uniform Commercial Code because it facilitates commerce when there is just one rule that all firms, regardless of originating state, must follow, instead of 50 rules. We have an EPA that regulates pollution standards because local authorities are too easily influenced by local businesses who can threaten to leave if not appeased. We have national drug and food testing because it's far more efficient.
The hard-right thinking that everyone was just fine and happy until the big bad government decided to feed the poor; regulate food and drugs; provide federal insurance on bank deposits; institute auto safety standards and mileage standards, to name a few.
The reality, of course, is that federal involvement is a REACTION to unwanted conditions. Government officials didn't wake up one day and decide to regulate drugs. We saw that certain drugs were hitting the market and harming people. Likewise with food regulations.
Anti-poverty measures were created because of recognition that the market does fail certain people. John Kennedy was amazed that when he campaigned in West Virginia, there were starving Americans.
The right-wing likes to mask all of this under the label of "freedom." Federal government policies give Americans, freedom of starvation; freedom from illness caused by pollution; freedom from birth defects from untested drugs; freedom from economic disaster, etc.