Yeah, prosecutorial and police discretion on what to arrest and prosecute is actually the very source of much discrimination. Making it so all crimes must be prosecuted is actually a good thing I think, because it would eliminate that discrimination where some people slide while others are harshly punished.
Having so many laws that you cannot follow them all, but it’s not a problem because they’re not enforced is a problem! It means that the government can come after anyone at any time. Forcing all breaches of law to be prosecuted to the full extent without being able to set priorities would thus require the removal of many laws, which would be good.