A lot of these guys start with the function they need a circuit to fulfil and learn just enough to select and integrate it into the project, so at the block dia

A lot of these guys start with the function they need a circuit to fulfil and learn just enough to select and integrate it into the project, so at the block diagram level. In those cases learning circuit design is overkill when learning how to select one (from a circuit cookbook) by understanding functional and integration parameters, customising and modifying it after reverse engineering are sufficient. Akin to a course in driving rather than car design. Not sure how many books approach it that way but for a lot of people building fully customised electronic circuits is too much effort.