I feel like surely yours isn't a point made in good faith, because the point I'm trying to make is so simple.
If I've got $20 bill or a gold bar in my pocket, I can use it at the store if I can get to the store, but someone could easily confiscate it from me. If I have a $20 bill or gold bar buried in the woods behind my house, it can't be easily confiscated from me, but I can't use that at the store, even aside from whether I can access a store. If I have a cryptocurrency wallet, I can use it in the hypothetical cryptocurrency store if I can access it, and it also cannot be easily confiscated from me (assuming reasonable security measures).
The real criticism is "what cryptocurrency store?" and that's the real reason cryptocurrency isn't very useful. I'm not arguing that cryptocurrency is good or useful, I'm arguing very narrowly for one specific point: "owning cryptocurrency" is more like knowing something than it is like possessing something.