See, the 23rd century is interesting and nice and there is a huge gap between ToS and TNG, which makes for an ideal TV series, but we already know what happens after the show, so no new major species or threats can come, or they would be mentioned on TNG/DS9/VOY such as the Dominion, Borg, or even Ferengi. Plus the last prequal series turned into the disaterous Enterprise, but that may not be relevent. Enterprise could
make new alien species since it was so long before the other series, before even the Federation. The only problem with Enterprise was everything except some of the actors and the idea to show the first starship and how the Federation formed.
EDIT: BTW instead of post-voyager, I meant post-Nemesis.