as another pointed out, i feel you need a combination of expertise spanning "ops/infra" (often called devops engineers, though i don't believe in "devops" as a title), SWE (focused on solid development like building portals, writing custom operators, etc) and SRE (thinking about reliablity of the platform, SLI/SLO, observability and common SRE tasks). this is thinking about IDP at scale. to get started you can obviously have a lot less, but this "ven diagram" is the ideal combination in my mind for a platform to be sustainable as it grows with the right focus on features balanced with stability.

i also like this as more of a "what is idp" and how it might help understand a fit with titles in your organization: