It probably means having more buses and trains avaliable to use (by building more maintenance facilities and larger stations for interchange). As having one come every 4h is a bit rubbish and would put anyone off.
Public transport needs to be cheep, reliable, and often to work. You can get away with any two of these at a push. Public transport works in London because you know no matter when (within reason) you turn up another bus/train/tube will be there with 15mins.
A core problem in Wales' transport infrastructure is that it's very difficult to go North-South via public transport. The campaign for a North-South railway is something that's been going on for a while.
Currently if you want to go from Swansea to Bangor, Google tells me it's a 4hr 24m (155 mile) drive, but it's around a 5hr 20m-ish train journey that takes you east to Cardiff, then north to Chester or Crewe (in England!) before back west to Bangor - and if you want to go onwards from Bangor (e.g. to Caernarfon) then you're reliant on buses.
What that means in practice is that for international tourists we're basically saying you can visit Cardiff/Swansea/Gower/Brecon in the South, or you can visit Snowdonia/Anglesey in the North, but not both - whereas if they visit England then they've got more options.