Stellaris is a beautiful game. The best part is that multiplayer is so easy compared to the Civ and other games as you're never stuck waiting. Thanks to the "real time" playstyle you can always keep doing things.
That said, I always rule my galactic empire as a warlord for conquest. Simply because these games never really reward passive playstyles. For instance, if there is a habitable planet in another species borders that they can't and wont use themselves, there is no ability to trade for a system they don't use and no way to be given rights to form a colony there. Even with your own allies you can't share borders. So the only way to actually use all habitable planets is to conquer each other.
The game tries slightly to allow you to grow and use other planet types through technology to terraform or by getting different populations through migration treaties but this is flawed. Terraforming is expensive and time consuming and doesn't work once you live there. And migration treaties don't really feel like you're a "Individual supporting xenophile" race. Like where are the refugees, the outcasts, the greedy from other races who want to join you for their own benefit regardless of what their species government says?
The game is good, and most games do exactly the same things with the same pitfalls. But at least Stellaris is highly moddable. I've made my own and tweaked the game rules to my liking very easily. I highly recommend the game, even if it could always use improvement. Then again, most people don't want more from a game unless they're really passionate about it in the first place and want to see it fulfil all it's potential.