The game is fun, but I feel like it lacks a bit of the latest addition that "main" Stellaris has. On the other hand, if Star Trek Infinite gets even half the development post launch that Stellaris had, it will be absolutely great as Star Trek has more than half century to lore that can be integrated into the game, while Stellaris is all about being "the definitive sci-fi sandbox". Both philosophies are great in their own right, they just can't really be compared in my opinion.
One thing that Star Trek Infinite should already have in my opinion are different starting dates, as the canon has an established timeline. Lost of details should be addressed, like missing Remans and Risians, Bajorans not having a native planet, and I guess other species that are not placed on the map as for now but they should be, especially if they are too small to get a proper DLC on their own.
Somewhat, I got the feeling that Star Trek Infinite is a bit unpolished for a release, like the older PDX titles: strange bugs like Jenaway being of the player chosen nation ethnicity, Bajorans "missing their homeworld" or science ships being unable to avoid automatically reality rifts make the game seem "rushed" and not tested enough "in-house" before the release. This is a pity, luckily, Star Trek is a long standing fandom, so there is all the time to fix these issues, still, the game would have felt better if immediately visible bugs would have cleared before publishing.
I also miss the galaxy size slider and the possibility to set the endgame date.
Planets looks so much better on Star Trek Infinite than in Stellaris: habitable planets don't have exactly the same to be fully habitable. Just in an unfinished campaign, I've seen at least four different types of "M class" planets that can be inhabited, all staying graphically diverse with no need to alter your species or do terraforming to have that 100%, and from a roleplay perspective, ruling on planets that actually look different from each other is quite great.
I think that Ferengi, Breen, Orions and the Dominion or playable Borg will get their own DLCs in the future, so the galaxy will feel more populated in the future. Ferengi and Orions would feel great as Infinite equivalent of the Megacorp DLC for base Stellaris, the Borg will be for the Syntetic Dawn equivalent and Breen and Dominion should be great for a specific "DS9/Dominion War" pack.
The sound is unfortunately, where Star Trek Infinite can't compare to classic Stellaris. The music is too low, the music sliders aren't enough to make it clearly audible, the voice acting while is probably not bad as some have described it, is clearly not Star Trek material.