When I was doing hardware in the 80 early 90's I came to the conclusion that the 'reusable code' fans were all missing a point.

You are either writing a library,a framework, or something like that. Or you are implementing some 'business logic'

The point of the former is reusability. The point of the latter is utterly not and you should not waste your company's time and money or worse let schedules slip because of it.

Some further thoughts over the years.

Reuseable code must have a public, well designed, sable, and documented API or it won't ever be reused. Be honest how many programs are going to reuse this code? Enough to justify all the above? Didn't think so.

One of the problems with reusable code is dependencies. OOP code bases tend to have more than the ordinary number of dependencies.