Agreed. I grew up on MOO2, played too much of it, mostly hotseat with a friend.
I tried a few other 4X space games, but none scratched the itch that Stellaris did. It's the only 4X space game I play now. And Paradox keeps adding content!
The late game crisis is such a good idea to solve this problem.
At that point you're strong enough that you can beat all the other empires but then an extra-dimensional invasion happens that's just so much stronger than anything else you've encountered and it works really well to spice up the late game and make everything relevant again.
Stays relevant until the very end.