I disagree. The UX design is a critical part of the design language of a game. The Settlers has a completely different setting than Assassins Creed or The Division. For The Division a “cold” and technical UI feels fitting, since this matches with the world it plays in. For Assassins Creed it’s a mixed bag, but since the back story in AC is also extremely futuristic and technical, it still fits. It would likely still be better if the UI was more aligned with the main-setting of the game than with the background-setting, IMO. And finally The Settlers doesn’t fit at all into this theme, yet the UI still looks like it.
Re-using the engine and the development tools is completely logical and a good thing. But the UX should be in line with the setting of the game, not the company that it was developed from. Because that breaks immersion.