Imagine you are creating an app for people who grow rare orchids. One option is to find someone who is one of these people. The other option is to find someone

Imagine you are creating an app for people who grow rare orchids. One option is to find someone who is one of these people. The other option is to find someone who is very good at understanding people, and tailoring experiences to match. This is what UX researchers specialise in. Also, your app raises questions about clinical methods, not just standard UI/UX to solve for user expectations. It would be best for those methods to be designed in coordination with professionals highly trained in managing OCD and its symptoms. Which is another reason it probably isn't essential that every member of your team has personal lived experience of it.