Yes, they can be copied infinitely for free, but we're only "post scarcity" if we never make anything else new.
With the advent of generative AI, we might just barely be starting to be post scarcity in a couple narrow fields.
On top of that, significant amounts of stuff are created out of an internal need, and would get created regardless.
One thing I'm sure about is that we're post-scarcity in historical items, and we're nowhere past capitalism there. Indeed, preservationists are hitting roadblocks all the time.
I'm not sure I'd say we're "post scarcity" for books and other digital goods though. Sure, we have all the books written until now, but I think there's an argument to be made that a huge part of the utility of books is that they are produced in near-real-time to discuss, address, and reflect thecurrent state of society. As our society grows and changes, books featuring the issues of the days will always be desired. This falls into the "trends" category you mentioned, but my point is more that I think it's larger than you described.
If you could just generate energy out of the ether and use it to materialise food and anything else you might want, for example, that would be post-scarcity.
