Personally I think 4x games just try to tackle wayyyyy to much ground at once, and leave a game that's pretty mediocre at everything.
Look at AI War, it's a very scaled-down version of a traditional 4X. No ship design, no diplomacy (BECAUSE F YOU AI), no complicated trade routes or resource management, no worrying about population sizes or planet types, or how happy your people are on miserable Desert World, etc. Yet even being such a scaled-down version of a 4X game, which includes no competitive multiplayer (something that most 4X games attempt to include), it has still taken years of patches to work into reasonable shape.
I think a good 4X game has to be tackled by a company with a lot of resources. It's not a feasible Indie goal, yet Indie companies are the only ones attempting to do them.
After being somewhat disappointed with Stardrive, I just jumped into the latest Alpha of Starfarer (renamed Starsector), and I'm so impressed I feel like I could scream. I've always been impressed with this game, ever since I bought it like 1.5 years ago, but whenever I come back to check on it, it just keeps getting better and better. The combat is so simplistic and visceral, but also intuitive and dynamic at the same time. But that's because they aren't massively concerned with the traditional 4X concept. They want a good space combat game first, which they've pretty much accomplished, now they're moving to the single-player only campaign mode, which once again is not a 4X. And that seems to be moving along nicely as well.
So I feel like if they had tried to tackle a traditional 4X, the game would be a disaster. So instead they just made it a pseudo-4X, scaling down the elements and keeping the fun stuff, and I think the results speak for themselves. It's much better than any 4X I've played in a long time, and it's still in Alpha.