Actually Agents of Yesterday did not do so bad on the Original Series stuff.
There was some recycling of scenery/map assets of course such as the engineering rooms, but it was done a lot better than some of the earlier 23th century stuff in Star Trek Online like that space station.
I am more disappointed that it was just so short
But yes I understand your disappointment, I also had hoped we would have seen a new Star Trek game set in either the Original Series era or the TNG/DSN/VGR era, an action-adventure game with some puzzles and a good storyline and narrative.
The 50th anniversary of Star Trek has been game wise in general very disappointing despite this being one of those 'anniversaries' you really want to show your IP to as much people as possible. There is not even a silly little mobile game based on the new movie.
Well if you have not played them yet, try
Star Trek 25th Anniversary and
Judgment Rites on Good Old Games. (
Starfleet Academy is okay but it has not aged well)
Hopefully
A Final Unity,
DSN The Fallen,
Elite Force 1 & 2, and
Bridge Commander will become available one day for new gamers to enjoy.