A lot of great answers here, but there’s another possibility I haven’t seen mentioned yet. When you are gathering information like this it says to the engineer that you want to change things, and they don’t know if that change is going to make things easier or harder for them. Usually things only ever get harder as a project lives longer. So they’ll be less incentivised to help you unless you give them an idea of what you intend to do and specify what problems you intend to solve to make life easier for them personally.
Also, as an engineer, things like this I generally see as less important than making sure the product works and that development is processing on pace. Having to explain everything about my job to someone coming in with 0 prior knowledge is a huge waste of time.
One tip I saw mentioned works well in this situation: get them to start complaining about things they hate about the current processes. Everyone likes to complain because it is cathartic.
It will help if you can educate yourself before talking to them. Present the info you have and ask them to fill in the blanks or make corrections. Must engineers like to solve problems, so present this as one for them to solve like a puzzle. Engineers are generally not novelists. Don’t ask them to just start spitting out history of The Process to you.
Having eaten at McDonald’s in both USA and Europe, I can say the food quality is noticeably better in Europe.