In the past, search engine optimization was all about small hacks, technical bits like optimizing metadata and buying backlinks. SEO today has become more complex, giving increasing importance to every aspect of the visitors' experience, from how fast and well a page loads on a mobile device to how interesting the user finds your content or what they thinks of your brand.
SEO has become strongly interconnected with other Digital Marketing areas like UX, UI, Social Media, PR, Digital Reputation, etc. As writing a blog in the AI era, or getting some cheap backlinks, is no longer enough, you need an agency that has a deep understanding of the big picture and can provide a holistic SEO approach.