As someone who faithfully watched it on its first run back in the 80s, I'm here to tell you that outside the opening credits:
THUNDERCATS REALLY WASN'T VERY GOOD
Honestly, like most other shows of its day, it was a long-form toy commercial, selling action figures and vehicles, with a simplified plot for kids to re-enact with those toys. Granted, Transformers, G.I. Joe and Masters of the Universe were even more blatant commercials, but in the end that's what all of them were. Including T-cats.
@Nezchan
Totally agree. Even posted the same thing the other day.