In general those franchises taken back into public ownership have been better - timewise, profitability and so on. Network Rail are public - but hampered by the fact that they cannot do anything in a joined up fashion - as they have to meet the demands of the TOCs (and pay them for delaying services to carry out maintenance and so on).until Covid was a rail commuter for decades, enjoying the subsidy of cheap commute to London. problems with rail are down to management, operations and capacity, which wont change under a different ownership structure. as proven by so many franchises returning to public ownership and problems persist. Network Rail has been publicly owned since 2002! this is all besides the point, which is the notion that a top policy to solve the country's problems is rail and it's nationalisation. it should be somewhere way down the list.
Also - it's not going to solve all the country's problems, but it is one bit of the whole jigsaw.