The alternative algorithm would be better than DNN if the same amount of effort was put into creating special-purpose hardware, libraries, and so on; but in the dystopia, it's not fully refined DNN vs fully refined alternative algorithm, but fully refined DNN vs alternative algorithm with hardware and software optimized for DNN.

The alternative algorithm always looks unappealing because the playing field historically favors DNN, and so doesn't take off in the dystopia.

DNN emerges out from being an underdog. Its superiority was proven by technology and economy.

What you said is of course not wrong, but they can never be proven right. As immediately you switch the role, your argument then favors the other one.