Yeah, it was quite painful because we had to support UE4 under UWP, which was utterly broken. Also, both Microsoft and Epic changed a lot of things regarding Xbox/Windows User Management throughout development, conflicting with our implementation when there was no out-of-the-box solution available.
It should be less complicated now since we can work with an out-of-the-box WinGDK Unreal Engine version provided and maintained directly by Epic. The XDK integration and user management are in much better shape today.
That said, the submission process is still much more complex technically and bureaucratic than on Steam or GOG; there are still quite a few things to do for making it through Microsoft Certification, so updates on the Windows Store will likely be a few days behind.
To be clear, though, "until they finally decided to remove the game from there" is NOT true: https://www.microsoft.com/en-us/p/everspace/9nblggh4sf90
/Michael