Does the design / CMS of the site affect the promotion?

Question

CMS

The question is a bit general. Let me explain.
There is a site without CMS, self-written.
Hence:
- pages with different designs (for example, 1 , 2 , 3 )
- lack of any clear structure by sections, which would be displayed in the menu, breadcrumbs, etc.
The second point is definitely important for SEO, but how best to implement it in a self-written site? "Decompose" page files into folders of sections on hosting? Or is the "correct" link structure in the menu enough?
And how important is the first point with different designs, fonts and no CMS at all? What other problems can be on such a site?

Answer 1

But the structure needs to be made and bread crumbs. Yes, you can organize it into folders, but the structure in the menu is also required.
It doesn't matter if the design is different.