People think that constraints limit creativity. The truth is that real creativity only flourishes with constraints.
In both the print and the digital world, tiny elements or fine lines cause real problems in logos.
The word "design" implies care in rendering. There is no place for sloppy work in identity design.
Overlapped elements was common more than a hundred years ago but those companies figured out that it reduced legibility. It still does.
Any part that does fit with the other parts is wayward. It may also create the wrong mood for the company.
It doesn't matter what you've designed if it can not be seen. Contrast is a physical reality rooted in value.
Lack of mass will make a logo harder to see, especially at small sizes or at a distance, while those with good mass are easier to see.
Multi-color or 3D logos are not bad, it's just not where you start. A well designed logo, one that works in solid black, can always be embellished. The reverse is often not true.
How many holes does it take to ruin a balloon? Only one. How many deadly sins does it take to ruin a logo? Only one.