One big hole in his (and Moldbug's) "there can only be one" theory, is that if a merchant only accepts BTC and I have only an altcoin, then assuming liquid exchange markets between the altcoin and BTC along with clever programming, I can pay with my altcoin at that merchant with one click. So there isn't any cost in terms of market mass to being not first in the market.
Just going to take a stab at this one thing here but, doesn't this imply that
1) someone has to use the resources to run such an exchange, when the alternative is to not waste those resourses and use Bitcoin
2) there must be enough other users to make the exchange liquid
3) one of you, probably you, has to go through the trouble of setting up an account on such an exchange, and software on your wallet, when it is easier to simply use Bitcoin
Essentially, while yes, the system can be patched to work, there is still the issue of fighting against the established system (using extra energy and resources) instead of simply capitulating to the lower energy-state system that doesn't have the extra friction.