But the line most posters have been peddling is that the lack of the railway has deterred visitors to the Island, most of whom will be wanting to go to the front area of Shanklin or Sandown - so you need to make up your mind.
As for your comment about 'useful for a lot of people' - let's unpick that, Sandown's population is about 12,000, Shanklin's is about 9,000 and Lake about 5,000 - so sub 30,000.
Looking for somewhere comparable - if you took Sheringham and Cromer (both coastal resorts, both with a line heading to one key destination etc), you've got a combined population of circa 15,000, but a combined usage of their stations (using 18/19 so as to ensure no Covid impact) of about 0.45m / year. The Island line across Sandown, Lake and Shanklin is about 0.44 - on double the population. Not sure that passes as 'alot of people'.