Strongly disagree. That may be true if there is no good way of getting information, but once there is a website/app that lets you enter your source, destination and departure time, and which clearly lists all the options with their prices, people do effectively shop around and make rational choices about their routes. This has been shown to work pretty well in Finland.

The clearest example is probably Hamburg-Köln-Express in Germany, which operates trains that take around the same time as the state-owned incumbent (DB Fernverkehr), but on older rolling stock for a lower price.

The hard part is "how do you divide up the capacity on the infrastructure", but this is a problem that has clearly existed throughout the EU since 2007 (when there's been open access freight operators), though has in reality existed much longer (most international services, for example) hence track access and allocation being the subject of an EU directive all the way back in 1995.