Honestly, I find it difficult to believe that all, or even most, of the Federation ships other than the Enterprise were of pre-2233 design. Why would the entire available squadron at the heart of the Federation consist of quarter-century-old ships? (Unless they simply haven't been building new hulls for a couple of decades, for some reason, and Enterprise represents the first new construction in a long time. But why would that happen?)
Also, if they're in existence that long ago and hence part of the Prime timeline's Starfleet as well, why aren't we still using suitably-refit monster ships for the major actions?