German trains were great twenty years ago. I wouldn't be surprised if things went haywire after lockdown. Many things did. It gave people a licence not to work and introduced a sloppiness into everything.

I'm fairly certain it was before that, as someone living in The Netherlands we'd always get warned to make sure there was at least 30-60 minute transit time between each stop in Germany when travelling international, as the expectation was that the train would be (extremely) late.

This was already the case around 2015.

Trains are still great. Especially the newer generation ICEs are beautiful trains and very comfortable.

Just don't count on them that they bring you to your destination in a timely manner.