I see both kinds of sets for sale. I do not see ruination. Both kinds present an empire of creativity when they're disassembled and mixed up together in a box, as tends to happen with Lego. It's fine.

Or, alternatively, it may be possible for a person to be such a profoundly grown-up adult to be unable to see it that way. If that's the case, then I guess you're right: These adults are incapable of being creative with Lego, and therefore adults have ruined Lego. For themselves.

But if that's the case, then it was ruined for the old coots from the very beginning. :P