...變差了許多。而開在某 Food court 的那分店更是...

昔日老伯伯坐鎮時與現在實不可同日而語

You can try these steps for better effect:

1. Steam it more than 3-4 hours with low or medium heat (This way you may  even chew on the bones easily)-- I often steam it right after lunch time and serve it right on  time for dinner at 7pm--i.e. almost 6 hours.

2. Add water into steamer every now than then (To increase moist and to prevent burning.)

3. Sprinkle water on the surface of the rib at least  3 to 4 times during the process (So that more juice flow down to the sweet potato underneath.

4.You may replace sweet potota with sweet yam, it's even better.

FYI-- I enjoy watching the food you introduced, and will definitely try those restaurants next time in TPE.