Not to belabor a point, but how do we know that those prototypes and other ships weren't at Wolf 359?...but how do we really know that the unnamed Excelsior prototypes did not participate?
We don't know that those ships participated any more than we know that the rest of the fleet was composed completely of Nebula class ships. Some people seem to think that because they were seen at the surplus depot, they were from the battle because other ships form the battle were there as stock footage. So does that mean that the two spacedock study models, the two Talarian freighters, the two Talarian warships and the 'V" miniseries saucer were at Wolf 359 too?
Based on what I can see (8 Galaxy family ships, one Ambassador, one Excelsior, one Miranda (with updated interiors), one Oberth, one shuttle from presumably another Galaxy family ship, and what hasn't been conclusively proven to be a fully intact Constitution), it appears that if this sample is a representation of the entire fleet, then it was probably composed mostly of more advanced ships from the 2350's and '60's, while the older designs tended to be less, but still hardly "antiquated."