I think the implicit question is not "why aren't Soviet-era military jets competing with modern cargo planes?", it's "why isn't a modern version of this competing with modern cargo planes?". (The former is just comparing 1970s apples to 2010s oranges.) In this context, it's reasonable to assume a landing gear and modern engines.

Re: the Antonov, I think the idea is that it needs to be very low to utilize ground effect, and the only way to do this safely is over water with a hull capable of emergency water landings at the very least.