I think the problem is that theres a distinct epoch that each ship belongs to, thus when ships are with members of the same epoch, they feel like they belong and by extension if they're in different epochs, their differences are highlighted
More ships that "bridge" the epochs would help, a broadsword is at home both in a lowtech and midline fleet, as is a mule or a venture whereas an apogee is between the midline and hightech, all these ships both provide a middle ground between epochs and make the entire fleet seem more coherent imo