The most significant difference between a traditional approach to product & service development, is, that in Lean, we use a so-called Product Mindset to tackle the challenges, we want to solve to our client.
The goal for a product (and therefore the product mindset) is to add continuously value to an existing product and service. The journey is the destination.
The goal for a project (and therefore the project mindset) is to achieve the project goals and then to start a new project. The destination is the purpose of the project.
In a product mindset therefore, we are constantly looking on how we can improve something, that exists without thinking about where this might end. Our mind is geared more towards the improvement itself, than to achieve a certain goal. This is key in a lean approach to lean product & service development.
One of the biggest challenges, when we are constantly trying to add value is, that at some point our ideas (from ourselves, our stakeholders, our customers, or others) will eventually pile up over time and to prioritize the ideas to be added to our product or service will be more difficult with more items to have. Therefore, one of the most important skill of a lean product Manager is the art of saying no. Many Product Managers, who are hired by other people (e.g. Founders or C-Level) with struggle to see the importance of saying no because the vision and the goal for the product / service or feature is not 100% clear to them, so it is hard to make arguments for a cause.
But with saying no (thanks to data-driven arguments), a product manager can stay on course and focus on the features and value on the most important customer value overall. Experimentation and quick feedback cycles customer focus using a customer-centric approach is important in a lean product mindset. Lean means in the end to have a product, which is customer-centric in it's core (without having any waste) on top of being able to continuously improve. For that, we need to learn from the customers what they need and adapt the product constantly. An approach to gather data through experimentation or design-thinking will be supporting a lean mindset greatly.