Yes Shengsi is beautiful and not super crowded, but only because it is remote and hard to get to. Be prepared to make an arduous journey. You can do it as a day trip, but make sure you understand you will only be able to spend at hour at the actual beautiful village. Otherwise, you will have to spend the night. This trip is will set you back at least 600 RMB.
7:30 (1.5 hours, 144 RMB) Bus from Shanghai Nanpu Bridge Long-Distance Travel Building (Nanpu Bridge metro station on line 4, exit 1) to Shengjiawan Pier, make sure you get 联票 or combination tickets for the bus + ferry
9:00 (50 min) Ferry from Shanghai to Shengsi Island (Xiaocaiyuan Pier), buy return tickets and tickets to Guoqi once you arrive
11:30 (1.5 hours, 100 RMB) Ferry from Shengsi Island to Guoqi, buy return tickets once you arrive
1:00 (20 min, 150RMB for 5 people two ways plus 1 hour wait) Taxi from Ferry to WuRenCun (无人村）
1:20-2:30 Frolic around abandoned city
2:30-2:50 Take taxi back to pier
3:00-4:30 Ferry from Guoqi back to Shengsi (other port)
4:30-5:30 Dinner in Shengsi central
5:30 (10 min, 28 RMB) Taxi from Shengsi Central to Pier
6:00 (1.5 hours) Ferry from Shengsi to Shanghai
7:30 (1.5 hours) Bus back to Nanpu Station
The earliest boat back will be in at 11 am next day. You don't need to book a hotel until you get there in Guoqi. No one really speaks English, so it’s better to know some basic Chinese or ask a Chinese friend to help you out.