The reason it still took over the macroscopic world is that evolution does not simply select for reproductive fitness
Here I define reproductive fitness as the average ability of your genes to reproduce
I think this is false by definition? The thing evolution selects for is the ability of genes to reproduce. How are you using the terms here?
Workers are only sterile in the most eusocial of species. In others, being a worker vs. queen is something of a choice, and if circumstances change a worker may start reproducing. There isn’t a sharp transition between cooperative breeding and eusociality.
Even in very eusocial haplodiploid species (so ants and bees, but not termites), unmated workers may reproduce after the death of the queen. They can only produce sons, but it’s still reproduction. .