Actually no. German trains are often late, true, but outside of that its actually very nice. There are a lots of lines and lots of collections. The only time its a bad idea is if you have a real time constraints.
Yes but many trips don't have real-time constrains or only with local transit. If I go to city X and I need to go somewhere usually in X there are trains every 30min or trams to get me to my hotel.
But granted if you have a connection with two ICE depending on each other, this gets more problematic. Believe me I had that multiple times, and I was late but usually the next train is also late so it works out.
You can't plan super time constrained, but mostly for me it has been fine if you go in with that expectation.
Again, not defending this overall, in Switzerland I plan my journey I expect it to be on point, but I just dropped that expectation in Germany. And that fine for many situations, you just have to know that's what it is.