Stellaris excels at the appearence of customization. You have all these sliders to move and civics to pick and traits to count out at the start that you think wow, with all these options there must be so much variety and depth in the game!
It's only after you try more than three of them that you realise they don't actually do anything strategically substantive.
...which was the gist of the rest of your post, so TL;DR I agree.
If you were designing a grand strategy game around the question of "How can we get the highest number of upvotes from casuals and reviewers who won't play more than 10 hours", I kinda feel like Stellaris is what would fall out.
It's ironic when you remember that Stellaris was the first time Paradox included a Crisis mechanic specifically designed to jolly up the lategame, but there you go.
I highly suggest the Expanded Civics-Ethics mod on the steam workshop. Someone actually fixed this problem because PDX didn't feel like expanding on it.
Now it's far more interesting with the mod. I can't play without it anymore.