I had a site with 6,000 words of content on the homepage and another 30 pages of content all with a perfect silo structure, perfect keyword density, tons of images and dozens of videos on it.
I had something urgent to do so I let the site as is. 6 month later when I checked the site to continue working on it, it’s position is 0. Nowhere to be found.
Your argument is invalid.
Onpage seo is like the foundation of a building. You need a strong one to build higher floors, but if you only build a strong foundation and left it like that you will only have a basement and zero floors.