Yes, but the key need is to reduce the number of short journeys by car, replacing them by walking and public transport as appropriate, rather than necessarily longer journeys. This can only partially be addressed by railways.
Modal shift for existing journeys is far more important than meeting demand for new ones, for obvious reasons. That is not delivered by making all public transport free.
Workplace parking charges, ultra low emission zones, low traffic neighbourhoods, closing off roads, road pricing are all policies which influence modal shift, without making public transport free. However, they are generally criticised by influential lobbyists as a 'war on the motorist'.
Carbon emissions reductions, whilst important, are only one issue though. There are the issues of building the economy and enabling people to get to where they need/want to be. This involves longer distance travel as well.
I agree, free rail travel isn't the answer, but the current war on rail passengers isn't the answer either.