That list was a little farfetched. The most decorated Captains in Starfleet history, "living or deceased" (per Saru's order) are:
- April, Robert
- Archer, Jonathan
- Decker, Matthew
- Georgiou, Philippa
- Pike, Christopher
Now, this is in alphabetical order, so it's possible that the list extended past Pike, into the Q through Z range (so we might get A.G. Robinson or T'Pol or Shran), but the huge gap between G and P makes me think only a couple, at most, names will be on the list.
Based on Saru's exact order ("Computer list Starfleet's most decorated captains, living and deceased."), one would think the list should be by decoration, meaning Georgiou edged out Pike, and somehow April is a wunderkind who has more decorations than anyone in Starfleet history. The prevalence of "modern" Captains (4 out of 5) could be because of an increase in decorations compared to the earlier days of Starfleet.
But if we take the list at face value, that it is merely a top 5 list in no particular order, we face the fact that all of them are humans, and three of them were Captains of ships named Enterprise. They're all white guys too, except for Georgiou, but that's a byproduct of relying on reusing names from the classic series (and Archer).
Georgiou and Pike don't appear to be Starfleet's most decorated Captains, and Decker didn't appear to hold that distinction in TOS, but they could be humble about it. Garth is missing, but he might've been edged out by Pike, and he lacks a first name to easily insert into the list for consistency.
Maybe it's because all five never made it past Captain (disregarding Archer's future bio, and assuming April and Decker have yet to be promoted to Commodore), and most highly decorated Captains become Commodores and Admirals.
They should've tossed some new names and aliens on the list. It's a large organization and a big galaxy, we shouldn't be so familiar with every name that popped up.