If I understand the article, a similar assertion would be: "Because multiple inheritance is used so infrequently, the onus is on the designers to show that the complexity is worthwhile"

That's obviously not true, though - these things add complexity to a codebase and are best avoided until the benefits they provide outweigh the increased cognitive load necessary to deal with them when something breaks.

I would intuit that if the more complex features of a language get very little use, then that's the sign of a more mature and thoughtful developer community that emphasizes readability and simplicity.