Although an investor won't delve too deeply into your project, as they have numerous portfolio companies and can't afford to dive into each one, they possess a superpower—a vast purview. You will see them offering a "fresh look" grounded in extensive expertise.
Most investors have experience running their own businesses, having evaluated hundreds of companies they invested in and thousands of companies they didn’t. Their writings-off are also valuable, they know for sure what doesn’t work. They've seen the development of businesses across different markets, both locally and globally. This experience enables to see what’s coming next, to recognize challenges you might not see yet, and identify opportunities for success that you might overlook. Sometimes, your investor has a blueprint of the solution you seek because they've encountered similar situations multiple times.
Despite you, as a founder, remaining responsible for your project's traction and success, a motivated investor may support you in every aspect of your startup, from your business and financial model, marketing and sales, to team management, and improving your business processes.