Your portfolio will grow exponentially over time due to compounding. So will the embedded fees. Those fees include both your advisor fees and the fees for the funds used.
Advisors may help provide value by helping you set goals and motivating you to save more. They can also help by standing between you and the sell button in a market downturn if your emotions are derailing your plan. It assumes you can set goals, save, and make a simple plan that you stick to. You can adjust the behavioral gap input to account for some sub-optimal behavior.
Higher investment fees are a strong predictor for worse long-term performance and performance usually lags due to their fee-drag on returns. In fact, an actively managed fund that has recently led tends to lag moving forward. This calculator assumes active managers are able to match the market net of their fees. Here is an article that introduces some the concepts behind the calculator.