With today's technology why is there still so much confusion about moon sighting? do we physically have to see the crescent or can it be calculated as per orbit?

I don’t think there is too much confusion. It’s about the understanding of the teachings of the marja we make Talqlid of during the major occultation of the 12th Imam. According to our Marja Ayatuallhi Sistani, one should physically see the moon and must have two just witnesses.