That is very well put. I am often amazed what a big difference certain ideas make it possible to build complex things quickly and with low amounts of bugs. For example building a parsing subsystem "properly" as taught on compiler courses vs haphazard combination of regexps. It is mentally much more demanding, and requires more effort up front, but then to your surprise, every change you make just works almost immediately, and there are no hairy corner cases to resolve (this is kind of declarative vs imperative, but not quite). Another example is mathematical models, such as Markov Models and the like, where you can have a really complex behavior, but your parameters are simply matrices and all operations are some sort of matrix algebra. Difficult to understand at first, but very powerful and "clean" once you do.

In contrast, as you say, there are huge amounts of armchair ideas that are not worth very much even if they are correct. For example "software will eat everything" is something I believe is mostly right. It is also a business idea with direct implications for action. Despite this, it is only valuable to set the general direction (let's do software), but not any specific cases. It does not mean that every case of transforming a traditional business into a software one is going to be a grand success, or even profitable. In fact, these types of ideas have a tendency to cause one to forget the exceptions from the rule, and thereby being actively harmful.