1ST of all, VKM IS a trained wrestler.
Before becoming a promoter, he trained to become a wrestler.
Secondly, in pro wrestling, there are no excuses for poor matches, even for semi-retired wrestlers like Bret Hart or Hulk Hogan.
Undertaker vs HHH in a hell-in-a-cell was unique, because it featured some stuff that hasn't been seen in a while, like blood, for example, in addition to a match that had great ring psychology and constant suspense.
Also, whether or not HHH juices is not relevant to the case at hand. Scott Steiner obviously juices, but that does nothing for his actual in-ring ability, as he is still and always will be a crappy wrestler. Besides, pro wrestling is not even real athletic competition, so juicing is not even a factor in this case.
Anyways, WWE has a wellness policy, so there is no way that HHH could juice even if he wanted to.