3B1B - Welcome to the board!
Jr. Day/Unofficial visits are usually as good as you make them. They give you an opportunity to talk briefly with the coaches; tour the school and see inside dorms and classrooms, etc.; and ask whatever questions you have about admissions and their baseball program. Some can be made up of large groups of recruits and others are smaller and more personal.
Are they important in the overall recruiting ... No, players will be recruited by a school regardless of whether they have attended junior day. Going accomplishes 2 things: Shows the school you are interested in them; and Allow you see more of the school so you can finalize the list of colleges you are
really interested in. Both of these things can be accomplished in other ways. But, IMO, if it is possible to attend Jr. Days at the colleges you are interested in, GO.