I’ve been using neem oil for the last 3-4 years and it seems to do it’s job. Never had much of a fungus or mold issue in the garden, but do get insects if I don’t spray every few weeks.
The one thing I have found that neem oil doesn’t protect against is caterpillars that bore into the root stem then eat their way up the plant. Those destroy my cucumbers every year late in the season.