The initial part of the site is really bad advice. Dismissing utility classes upfront due to lack of knowing meaning is naive; every code base has a learning curve and making developers write a grid class for each component is not maintainable due to its time cost.
In my experience, a module/component heavy system with opt-in utility overrides has been the most practical and maintainable. For example:
Some things I do agree with:
Some flaws I see in the examples provided by the site:
For those curious, I use typically Inuit.email@example.com (6.0.0 exploded itself into little packages which it looks like it’s started to undo) with BEM and OOCSS mindsets: