[A_D_E_P_T]

Most modern mathematicians are not set theorists. There are certain specialists in metamathematics and the foundations of mathematics who hold that set theory is the proper foundation -- thus that most mathematical structures are rooted in set theory, and can be expressed as extensions of set theory -- but this is by no means a unanimous view! It's quite new, and quite heavily contested.

[housecarpenter]

My impression (as a dilettante programmer without relevant credentials) is that there isn't really any question about whether mathematical structures can be rooted in set theory, or can be expressed as extensions of set theory. Disputes about foundations of mathematics are more about how easy or elegant it is to do so. (And in fact my impression is they're mostly about subjective, aesthetic considerations of elegance rather than practical considerations of how hard it is to do something in practice, even though the discussion tends to be nominally about the practical side. Quite similar to disputes about programming languages in that respect.)

[nathias]

yes of course, I just mean that from the set of foundational mathematics, set theory is the strongest one empirically, but that there are other options (possibly better)