Here is a particular element from Mr Albert. This is html render of an invoice object.
This is how it was originally.
Here is an improved version of it.
Both versions are build using vanila semantic, but between them there is a massive difference.
The improved version, inspite of having more information is still more easier for the human eye to scan and find the right information. This idea of organising information to make it easier for humans to read is called information architecture.
In this case the new version is better because
There are some principle associated with information architecture. But the main one is
dont make me think. The less cognitive load your website is, the more easier will it be for your user to get value from what ever you are delivering.
As a single person founder, it is important to nail down your information architecture. Nailing this, is more important that various stack choices, scaling choices, theme choices etc.