Is there something wrong with just push blocking it and backdashing it then?
Yes.
The entire metagame surrounding f23 breath with most other characters is that they have options like poking or back-dashing and whiff punishing that Superman doesn't want to get hit by. Those options encourage the Superman player to go for something other than an immediate f23 follow up(a dash, pausing to make a poke whiff, etc) but if he does and the other play had decided to just block that provides another opening for Supes to get punished or at least for the loop to end.
Pushblocking gets you at out of the loop immediately without the guessing, and because of that is good situationally, but as a go to option it's useless. It does nothing to discourage Superman from getting in f23 range and starting the loop again and continuing the loop until he gets bored or Ares takes a risk. If you pushblock Superman loses nothing, he doesn't care. You just spent meter and didn't hurt him. It doesn't set up the meta-game I described above.
If Ares could keep him out better it might be ok, but Ares mobility is awful and his zoning is slow - one ducked or jumped fireball from midscreen means you have to block f23. You're not gonna build signifcant meter or do damage before he forces you to block another f23
Once Ares blocks f2 all of his options are awful. It's not that f23~breath is a block infinite, it's that the risk reward on anything Ares does is horribly skewed
