Attitude is just one factor of many
Sorry to say, not in anyway. That is absolutely not proven, furthermore, is quite wrong as a rule
However, in many situations and areas, that proves to be a rule, but it's efficacy is limited in time.
As an example, as a sales coach, indeed my first step is always motivating (changing the attitude of) the sales teams. It really works for a while if you don't add something else. These other things usually involve training, planning skills, organization and others.
In management, one can call attitude the company's culture. When people know what to do and why to do it a specific way. That change is not as limited in time, but is always a product of many organizational changes for a better day to day practice.
Back to sales teams, top salesmen are proven to be almost all having more than 10 years practice (see Dave Kurlan's studies on sales on more than 500.000 salesmen).
This clearly proves that attitude is only one of many components in getting results. Although it's an imporant one.