The main issue of the german HSR network is that it stops everywhere.
Seriously, it stops at nearly every village it passes, wich makes it slow, inefficient and expensive.
Meanwhile a good HSR just only stops at major cities and doesn't need to stop, wait and go all that often.
That allows a good HSR to run much higher average speeds and people to arive faster at their destination.
Another issue is that trains here often are either overfilled or nearly empty here, a cheaper night ticket would probably help a lot as well.