Если не до конца понимаете как работают шаблоны с наследованием, используйте простые инклюды.
Из документации:
Common mistakes
Pug’s template inheritance is a powerful feature that allows you to split complex page template structures into smaller, simpler files. However, if you chain many, many templates together, you can make things a lot more complicated for yourself.
Note that only named blocks and mixin definitions can appear at the top (unindented) level of a child template. This is important! Parent templates define a page’s overall structure, and child templates can only append, prepend, or replace specific blocks of markup and logic. If a child template tried to add content outside of a block, Pug would have no way of knowing where to put it in the final page.
Из
треккера:
If your template has extends in it, it can only have other content inside blocks.
GOOD:
extends ./layout.pug
block content
div some content
BAD:
extends ./layout.pug
block content
div this content isn't inside a block
