Hello,
After checking the documentation for Page Tree macro shows 'Loading' indefinitely, I managed to implement a simple solution for those styling their content.
If you want to keep your page styling code and use the Page Tree macro, add a Noformat Macro in the very same section of the Page Tree macro.
The page tree will be successfully loaded, and the whole page (except by the page tree, obviously) will keep the style you created using CSS.
It seems kinda obvious, and it might have been solved already, but since that the Atlassian documentation recommended to remove the styling, I thought that a workaround would be preferred.