I can only speak based on the experience I have representing certain communities and based on my review of the empirical evidence. The empirical evidence shows that mandatory minimum sentences don't deter crime. Simply having a mandatory minimum sentence in the book doesn't mean that a prospective offender is going to see that minimum and then decide not to commit the offence.
The things that are going to help alleviate crime are investing in resources in the community, such as by addressing issues of poverty, over-policing and those kinds of systemic issues.
If mandatory minimum sentences don't deter crime, the harm that they produce, in my view, is disproportionate. We send people to jail for long periods of time when they shouldn't be going to jail for those long periods of time.