Most of my experience in UX is based in Design Thinking. However, when faced with a new project, do you keep applying Design thinking to the task or are you flexible in your approach? For example, would you turn to a Lean UX process if the project requires it or do you stick to your own principles of Design thinking as that is what you are most familiar with and you know works?
Design thinking is sometimes difficult to define but, at its core, centers around a collection of methods or tools focused on achieving a design solution. You wouldn’t necessarily have to choose between Design Thinking and Lean, or the user and the product, but rather how you apply your proven methods to the process of the greater team of which you are a part.
I tend to think that there is an approach or strategy that isn't necessarily fixed but has some common set of characteristics. And I would probably put Design Thinking and Human Centred Design in a similar bucket. By the way, you could probably say the same thing for Agile software development approach. So they are plenty of things that you can do that would still be considered taking a Design Thinking or HCD approach, and Lean UX would fit under that category.
Then you have a set of processes and methodologies that you can use to execute on those approaches and strategies, which have a more concrete definition or specification of what it is, such as doing customer journey maps or wireframes. And then there might be personal preferences or variations of those processes and methodologies that are largely based on your experiences and past projects. Unlike approaches, you certainly can't be doing customer journey maps and calling them wireframes (although you could consider it to serve a similar purpose to a storyboard perhaps).
I think Lean UX is a little bit confusion because the Lean methodology incorporates a number of principles (that have many similar roots to other process improvement approaches), but has been specifically adapted to the start-up environment (where businesses working in IT and digital economies seem to have really embraced). Because so many of the digital products and services are focused on customer needs to provide a competitive edge, it is not surprising to see HCD and Design Thinking also added to the mix, and hence you have Lean UX.
How do I navigate this kind of complexity? I try to simplify things by taking the processes that I have, abstracting it to the core outcomes I am trying to achieve and stripping out the dependencies (so that it is essentially agnostic of the technology and tools used to deliver the artefacts) so that I can apply it to the different types of projects that I am working on. As an example, one of the abstracted processes that I have when doing research is to come up with a hypothesis and validate it with actual data. Now you can apply this to a Lean UX approach by using simpler and more nimble research methods like guerrilla testing rather than large expensive user testing labs, but still stick to the same principles of formulating a research question, taking note of your assumptions and then trying to answer the question based on the data collected (and repeat if necessary).
I think if you can start adopting this type of thinking to your design process, you won't have to worry so much about adjusting your process for each project because you'll find that there is essentially a very similar way to solve most problems.