Again, semantics: 'Investments' are not required to be made on 'positive-sum' underlying assets. For instance, airlines may make an investment in oil futures (a zero sum contract) to hedge expenses that correlate with their fuel costs.
>Crypto and slot machines are not positive sum.
I think this the part where I link to a wikipedia page of a fallacy I don't understand/doesn't apply? /s
We can call it whatever we like. It's still positive sum. (That's the point of the part of the quote you omitted.)
Crypto and slot machines are not positive sum. That is a fundamental difference that separates them from investing.
> is no riskless portfolio
Straw man [1]. Nobody claimed this.
[1] https://en.wikipedia.org/wiki/Straw_man