I don't think anyone is claiming no digital advertising should be allowed on trains or at stations are they? I think what people are saying is that the advertising screens must be proportionate with the needs of the primary customer, who are the travelling public. People are paying an awful lot of money to use these train services so they should be treated appropriately when they want to be able to see live departures from all parts of the station.
Yes, exactly this. The problem is that the new departure screens don't work, and they've been told that multiple times. They provide insufficient information as there aren't enough panels, they're too small, they're hard to look at (because they use a design of screen intended for viewing at a distance for viewing relatively up-close) and their location causes passenger flow issues.
There's plenty more detail upthread on why they don't, and it is possible that a single one in the middle (rather than two) with more panels could work, but they don't as they are, they're useless.
They were also insanely expensive compared to something that would work in that location (a long row of maybe 12 or so 40-something inch LCD panels on a metal pole in the middle of the concourse rather than two of them). This would have cost low hundreds of thousands rather than over a million.