The person’s goals might not be spending a lot of time on CSS. Because a person who just does everything from scratch may find themselves learning about what FlexBox is or why your z-index isn’t working.

Going off of the two screenshots in the OP, neither of those were about frontend.

So if the choice is spending time designing a more human frontend or spending more time on the core product, I don’t fault people for choosing the latter.

Now if the core product also stinks, that’s a different issue.