You're the only one talking about business logic. By definition business logic is not the same as fundamental algorithms or mathematics. Inverting a matrix doesn't change.
A business wants to be able to change its logic to evolve how they do things. You keep trying to conflate these things but they are polar opposites.
What definition are you going on exactly? Nobody has said the phrase “fundamental algorithms” before you in the thread. Yes, I would agree that those are distinct from business logic. Nonetheless the actual definition of the word “algorithm” is not formally or universally agreed upon at all. I’m curious what definition you’re using and where it came from, if only because I now feel confused.
When something doesn't need to change, that's at least an established algorithm. Algorithms like sorting, partitioning, hashing, reduce, map, swap etc. are common and don't change. Mathematics like linear algebra don't change. They are fundamental elements of most nontrivial programs.
Sure, that part I agree with. But the stuff around it, i.e. how those fundamentals are used and composed, also qualify as algorithmic to me. It’s probably a lower-level definition than you’re using, because to me all programs are an algorithm of some kind.
I don't know what you are trying to say at this point. You were arguing that every part of a program changes and expands. It should be pretty clear that that is not true.