Seo: Site Quality/Number of Pages/Number of Sites?

Question

Search Engine Optimization

Where is it more profitable to invest in capturing the market?
Invest in the quality of the site?
Increase pages for low frequencies
Or make several sites
Just an example:
Our competitor, like us, is building houses. Our site is better. But he created a separate site about "foundations" (Those who receive an order for the foundation will easily receive the whole house after)
Our site is an order of magnitude better, but since foundations are not his main specialty, he takes away some of the customers, easily less quality but with a specific site . And why not do it after that?

Answer 1

Who is above you and your competitor ("Wikipedia" and "Aggregators" do not count - only sites logically similar to yours)? Are there generalist sites like yours?
If yes, then you most likely simply do not have enough optimization for this keyword.
If only highly specialized sites are higher, then you will have to create a separate site for the "foundations".