The entire system is built on checks and balances. For instance even a simple district attorney can choose to effectively nullify laws within his jurisdiction by not prosecuting violations - something that has regularly happened in contemporary times. Even the final check - the lone juror - can also nullify laws by similarly choosing to acquit alleged violations regardless of the evidence.

You could obviously create a far more functional system but it would probably be far less stable. The reason you have all these checks and balances, from top to bottom, is that the Founding Fathers were obsessed about the risks imposed by both a tyranny of the majority and a tyranny of the minority. And non-enforcement of something effectively comes down just a continuation of the status quo, making it difficult for any group to [openly at least] impose their will on others.

Theoretically that's true but in practice there is ample precedent for Presidents refusing to enforce specific laws. In one instance (DACA) the Supreme Court ordered a President to continue a previous President's official policy of not enforcing certain laws against certain people!