In another attempt to vaguely drag this back on topic, it does raise the question about what the rail system is expected to provide.
I don’t really think it is remotely realistic to expect heavy rail to be the main mode for people’s shopping trips.
In the case of the Island, the existing line is potentially very handy for funnelling people into Ryde and to the ferry. The only future extension that would make sense is along the Ryde-Newport-Cowes axis which would cover the largest traffic flows and give the maximum benefit in relieving traffic. But even this would struggle to be justifiable given the likely high expense.
There are probably many schemes elsewhere that would better justify taxpayers’ money. (And this is where saying ‘I don’t care about anywhere else’ doesn’t work, as like it or not everywhere else is competing for limited investment resources)