In my opinion, your today's conclusions about the value of cryptocurrencies are fair, but ... There is some truth in the words of your opponent, in my opinion. Sorry, but I'm interested in reading and commenting on you, and not approving all your thoughts.
Perhaps the opponent is talking about tokens that have turned into nothing and were originally nothing? Remember how cryptocurrencies were shouted from every iron a few years ago?
So, in my opinion, in the end, cryptocurrencies from the top ten will survive, and all the rest will disappear into oblivion.
He is talking about the Eth gifs and images.
Which top 10? In value, or usage? There is a difference. I think though, that crypto is going to expand into the tens of thousands of tokens, using various connectors for interoperability to combine them.
Did your opponent talk about Ethereum? This will change the case. Then he is definitely wrong.
By value, of course. And not from a dozen, but from a hundred. Although, it is quite possible that there will be up to 500 different connecting tokens.