still not clear what purpose of heading tags is

check what your theme does too. plenty of wordpress themes wrap sidebar widget titles and footer bits in H2/H3, so your outline ends up full of "recent posts" and "follow us". won't sink your rankings, but it's a mess for anyone using a screen reader and easy to fix in the theme settings or a child theme.

think of them as the outline of the page. H1 is the title, H2s are the main sections, H3s are subsections inside an H2. screen readers use them to let people jump around, and search engines use them to understand what each part of the page is about. the common mistake is picking a heading tag because you want big bold text. that's a styling job for CSS. use the tag that matches where the section sits in the outline.