> A program must be maintenable, efficient, observable, testable, scalable, performant, readable, secured.

This is the key that most people miss.

The second thing most people miss is most of the time efficient, scalable, and performant are good enough. Not always, there are no absolutes, but most of the time you can safely compromise those 3 without any problem that the real world will notice. In general maintainable has proven to be the hardest/most expensive, and so clean code is most important (don't confuse with Clean Code as a book or any set of rules puts it). Indeed, observable and testable are just different ways to express maintainable. (the first is you can understand what went wrong, and the second you can ensure your changes don't break something else).

Secure is the final thing I didn't mention. this is becoming more and more important. It may even become more important than maintainable in the future.