WordPress theme plugin

In the theme requirements section it was written, use lateral plugin.
I don’t have any plugins and all the sections are inside the theme. Is it mandatory to use the plugin?

At some point you’d need to use some plugin ( core theme features at least ) if you’re asking for development.

I do not understand the reason
For example, for metabox or any other feature, why can’t I create it inside the theme?

I saw this page and asked this question.
Just tell me this. If all the features are inside the theme, will the template be rejected?


Thank you