Dots tend to not be very good either when picked green (to be honest, I am in a "group" that believes mangoes picked mature green tend to not show their real potential). If mangoes bleed milky sap when picked (the more sap the worse off you will be), mist likely was not ready and will not ripen up properly.
With that being said, sometimes picked full ripe from the tree can be past prime quality. I believe there is a right time to pick each variety and it varies from variety to variety. It takes practice and time to find the sweet spot.