The BREXIT vote asked if Britain should or should not leave the EU, it did not give the Tory Government the mandate for anything else.
Starmer is very rightly making moves to undo the vandalism perpetrated by the Tories against the best interests of the UK wrt to the EU.
Good luck to Labour in those respects, the Ik economy, UK businesses and the people of the UK can only benefit from improvement in UK EU relations and trade.