[jerf]

You don't access the computronium. You move into it.

"good old-fashioned computing is interesting at all"

"Computronium" is defined as "the best computing power available". I deliberately selected it as a neutral term that does not depend on any particular model of QM or black holes or anything else.

Personally I doubt it's exactly one thing because optimizing for different types of computing is likely to result in a spectrum of computroniums rather than just the one, but the term flexes to encompass that easily enough.

The point is, you build something in that system over there for the same reason a normal human might buy a bit of property and put a house on it. The human in question isn't going "oh, I don't need to do that because the world already has hundreds of millions of residences". The human does that so that the residence belongs to them. The hundreds of millions of residences that do not belong to them do not factor into that question.