Can I just seo-optimize the landing page i want to rank high in Google, or do I need to mess with my whole website?

Hey.

I run creative studio that's rather minimalistic in the language used and I'm not particularly drawn to changing that.

However, i want to create service-specific landing pages and would like to seo-optimize those.

The question is - does my whole website ranking impacts the ranking of a single page (that is a landing page)?

Can I just optimize the certain landing page and don't care about the rest, or would I need to mess with my whole website?