Class D really excels for home theatre and electronica type music with the speed, bass grip, and clarity. Tubes not so good with that.
Acoustic music, jazz or folk...slower music with less bass impact is where tubes tend to excel. The tone or timbre is better as well compared to that leaner cooler Class D tone.
A hybrid system can overcome these weaknesses with a tube input in front of a Class D output. Great synergy if done right.