Great advice which I assume you follow to the letter.

Which is what happened next.

The point was that even in international trains inside Germany, announcements related to trains problems are only done in German.

I speak it fluently, including some variations, however most travellers do not.

I also remember there used to be ticket machines in NRW only in German, about 20 years ago.

As a German speaker, spoken Dutch REALLY trips me up because of small pronunciation differences in almost every word. Written Dutch is way closer.

The Dutch seem to understand German better, but my Dutch friends credit that more to education and exposure.

I'm German, I don't speak Dutch. But I was able to follow a Dutch tour guide in Den Haag just fine when she was explaining things in Dutch. She kindly repeated everything in English for my benefit (I was the only foreigner) even though I told her I understood her just fine in Dutch.

You have to "adjust your ears" a bit but I think if you know German and English then you can understand Dutch just fine if it's not slang.

dutch is a bit harder to understand. like some german dialects that not every german understands either, like swiss german, luxemburgian or friesian (also spoken in the northern parts of the netherlands), or plattdeutsch.

i grew up in austria and in the north of germany so i got an early appreciation for understanding dialects. yet learning dutch took me a few months of staying in the netherlands. on the other hand when i visited luxemburg people were shocked that i could understand them when they spoke amongst each other

Ironically, technically speaking, there are seemingly more similarities between British English, i.e., Anglican German and current High German due to various perversions and "reforms" of the German language over the last many decades, in order to drive the Germanic people away from each other.

If the EU were a serious and legitimate institution, there would be an effort to implement reforms that nudge English, Dutch, and present day German all towards better mutual intelligibility, NOT diversion from each other through perversion and "simplification", or what seems to be a pollution and destruction of the current German and Dutch language through what at least Germans have a term for, "Verdenglichung", i.e., the portmanteau of German (De..) and English, prefixed with "ver...", meaning the transformation or application of.

I speak fluently 6 languages, and a few dialects of them, how many do you speak?

I think you still should be able to expect a bit of accommodation on trains that cross country borders or go to airports.

The EU makes travel between EU countries as easy as travel between US states. You can just get on a train from Germany to Spain without any prior planning.

They can. But they should also not be assholes with everybody else. And no not just local trains, I got information in English exactly zero times when there were huge delays on international trains. And it happened 2 times from 3 when I tried to cross Germany by train. And Germans (and Austrians btw) are terrible with this, even compared to others. The German site at my multinational company at the time was the only site on Earth which had to introduce an internal regulation about mandatory English, because they just switched to German all the time even when there were people on the call from different countries. I’m living now in Wien, and they are terrible with this even in friendly environments.

It was an international connection train, ICE, between Amsterdam and Cologne....