[emn13]

Yep; I'm sure all these issues are solvable, and not just that - there are obviously workarounds in place even today (after all, you can make such trips). But the need to work around such incompatibilities (whether technically by using more complex trains, or logistically by altering your routes) has downsides. Those downsides make trains less competitive overall compared to other means of transport.

When people ask how planes can be competitive with trains, part of that is surely due to aviation's... interesting... tax situation; but part of it is due to real technical shortcomings in the European rail network.