I'm sympathetic toward the idea of a system made of interchangeable parts, but I also kinda feel like it's a bit unrealistic, maybe? Even with well-defined interfaces, there will always be interop problems due to bugs or just people interpreting the interface specs differently. Every new piece to the puzzle adds another line (or several) to a testing matrix, and most projects just don't have the time and resources to do that kind of testing. It's unfortunate, but IMO understandable that there's often a well-tested happy path that everyone should use, even when theoretically things are modular and replaceable.
