Yes, and international trains are not where the European network shines. It's getting better, but it has historically been hard to even figure out how to buy a ticket involving multiple countries. Deutsche Bahn is one of the better ones. If you originate or terminate in Germany, their booking engine can figure out how to get you to a neighboring country (and they actually have these countries' timetables in their system, too). But if you want to go through Germany, say from France to Poland, good luck getting that booked, unless you split it into two tickets, each terminating in Germany.

Specific through services make it easier a few routes, such as the CityNightLine sleeper services, since there is one train and one operator for the whole route.