Changing requirements requires changing code. I don't think it's a valid argument to say "we shouldn't take that approach because as requirements change we'll have to change the code". That's essentially software development.

You're misunderstanding me. Of course changing requirements mean changing code. The distinction is between a situation of "a small change in a requirement means a small change in code" and "a small change in a requirement means a BIG change in code". The make "make an enum of all the legal cases" approaches produces a situation where adding more binary conditions and requirements around them resulting in each change resulting a larger increase in code. And this in turn can result in a "we have to refactor this if we get one more change" and that's even more frustrating to those dictating requirements (and not uncommon in enterprise software).

Practically if you don't want to use enums and want another option, use a "builder" object. Pass in all of your booleans there and have it do you validation when you call its build method.

Cases are fine in some circumstances, enums of legal cases are fine in other circumstances and these builder might even be useful in a few bizarre cases. The main argument I'd have is that when one passes from "this approach can be useful, let's look at the situation" to "anything without this is bad", you often wind-up with a complete misallocation of resources and a fragile inability to make changes, as can be seen in today's legacy code (which was often yesterday's "best coding practices code").

I still feel like there is an important point you're walking past.

If there are 2^16 different combinations that are relevant, then you still need to handle these 2^16 combinations in your code. If you're ready a configuration file from a user and only different subsets of them are valid, somewhere in your code you still need all of the complexity to let the user know they have passed in an invalid combination. And all of that logic is equally or more complex than an enum.

If all of those cases can be handled by a few simple "if" in your code, then you'll have only a few valid options in your enum. If you have a ton of valid options you need to list in your enum, then you'll have a tone of cases you need to handle in your code.

Your underlying complaint to me sounds like you've received a lot of complex cases via your requirements. But either way the complexity is there in your code regardless of whether you validate it upfront in an enum, or deep in our code base.