Dave Ramsey gives good, old school advice. Not new advice. Not rocket science.
Many Americans are stuck in a consumer and credit lifestyle and don't have basic good money management skills or knowledge. They are over leveraged with consumer debt on depreciating assets.
Ramsey's advice is tailored to that broad group of people, generally.
People who are more educated on money and have financial discipline probably don't need his program because they are not setting things up in a way that is as risky.

Consumer debt that gets out of hand can cause financial hardship and can really strain relationships. Money issues and infidelity are the most common causes of marital troubles and stress in general. We live in a consumer world where stuff is deemed important and a status symbol. Too much debt and very little savings can be very problematic especially in an economic downturn, medical crisis where you can't work, job loss or downsizing situation, etc.

Advising people to be good stewards of their resources, live within their means, avoid debt, to save and invest wisely, and to give generously....in order to gain more financial peace in a person's life....well that is good basic advice that most people need. Not all people actually need to hear it from Dave Ramsey though. His style is not for everyone for sure. He's making tons of money through his show, books, training events, etc.

Plus I personally believe there is good debt (leverage) especially in real estate investing where the goal is cash flow and building generational wealth or on an asset that helps you actually make money. It's about balance and having safeguards in place to handle unexpected problems.