Stellaris feels like in a fair universe it would be a 7 out of 10, good but nothing to write home about games... Rather then one of the top 10 (or top 5) best 4x space games ever.
I definitely agree with this sentiment. In my mind, if you compare Stellaris to any other space 4X of recent time, it blows them all out of the water. That doesn't mean Stellaris is a good game.
The stories I can write about my Stellaris empires are far more engaging than the ones I can weave in GalCiv 3 or SotS or Masters of Orion, and in my mind, that makes Stellaris worth playing. It feels a lot like CK2 in that regard: I don't think I actually enjoy playing CK2 that much in the moment, but writing up what happened and telling my friends about it is a big part of what makes that game fun.
Stellaris is in an awkward spot where it's still very much beholden to 4X expectations, so it's lacking any form of chaos and as a result, things stagnate. Empires find their natural borders and just sit there. And they don't start to rot from within. There's no dramatic rising and falling of empires. I have never seen an underdog take on a superior foe and come out on top without my help.
I think I wanted CK2 + Vicky 2 in space, but instead we got this blend of Civilization by way of Endless Space and hey look we kinda have pops too. Victoria 2 actually has so many mechanics that make for interesting storytelling -- I hope some of them make it over in Stellaris' expansions. A deeper economy would be a good start. I'd like to see coups and internal revolutions too.