And how would you know what engine was the game built with anyway? If you're relying on the Unity log splash screen, then indeed you only see games developed by beginner teams who can't even afford a paid license.
Can't you tell? I can't tell the difference between Lumberyard, Crytek, Unreal (I could Unreal until 2012ish), but I always know a unity game because it looks and runs like shit.