...that being said, there is much room for improvement in the space 4x genre overall.
But Stardrive 2 is a very ambitious and it delivers, especially since it was developed by one person.
Essentially it is a remake or remaster of Master of Orion 2 with Stardrive draped right on top of it. Which is a good thing because MOO2 is still a venerable classic. Combine that with Stardrive 2 second to none ship/hull customization which plays a big role in ship combat and ship capabilities.
Ground combat: A simplistic xcom like turn based combat that while seemingly simple, still makes strategy, tactics and infantry loadout important and when used right, can enable a smaller force to successfully overcome larger one.
Diplomacy: Very similar to most other 4x, except with the smart inclusion of the tolerance meter, the dev now prevents the exploit of over-trading. Brilliant and much needed.
Spying: Pretty much just like in Master of Orion 2.
Critique/Negatives and room for improvement:
-Spying - too simple a mechanic with not enough options and abilities. Distant Worlds and Imperium Galactica 2 had a better more fleshed out mechanics and features in spying
Ship customization: the first Stardrive game used the entire un-sectioned hull with module access to power being a strategic requirement. Overall the battles in the first Stardrive were made more interesting due to the aforementioned.
Going back to Master of Orion 2: This is a subjective personal critique. Although the dev pulled it off beautifully in using MOO2 mechanics -- I had and would hope that future 4x games simply take note of features and use them in modern game mechanics that are no longer restricted by the technology of the Master of Orion 2 era. I would hope that future iterations of Stardrive build upon a real-time (pausable) open galaxy that the first Stardrive game was going for.
In a nutshell:
Space 4x empire games don't come that often. Good ones are rarer still. Thankfully, Stardrive 2 is one of those rare ones. I do at the very least recommend checking this game out further, if not outright buying it.