In what scenarios would it be considered a design flaw to use complex PHP constructs for styling elements?

Using complex PHP constructs for styling elements is considered a design flaw because it violates the separation of concerns principle, making the code harder to maintain and understand. Instead, it is recommended to use CSS for styling elements, as it is specifically designed for this purpose and allows for better organization and scalability of styles.

// Incorrect way of styling elements using complex PHP constructs
echo "<div style='color: red; font-size: 16px;'>Hello, World!</div>";

// Correct way of styling elements using CSS
echo "<div class='styled-element'>Hello, World!</div>";
```

CSS:
```css
.styled-element {
  color: red;
  font-size: 16px;
}