I need to stop treating an OO language as if it were a procedural language.

I have the tendency to turn my code into GOTO spaghetti even though I'm semi-aware that objects exist and that they are distinct.
I still have to get used to this paradigm.

My Java professor always swore by the Plato paradigm, i.e.:
""Platonism" and its theory of Forms (or theory of Ideas) denies the reality of the material world, considering it only an image or copy of the real world.
According to this theory of Forms there are at least two worlds: the apparent world of concrete objects, grasped by the senses, which constantly changes, and an unchanging and unseen world of Forms or abstract objects, grasped by pure reason (λογική). which ground what is apparent." (wikipedia)

Thinking in objects, abstractions and metaphysics is not something I haven't done before (I've practiced it during Sociology and Ethics with the whole Pascal Leibniz, Newton and DesCartes approach) but it's certainly not easy.

Then there was my cool Programming 201 professor who said: "Don't worry man, just read those great UML, Program Design and GOF books and it will all become easy, like a story. It'll all make sense.
I mean, I've graduated, I've passed my Software Engineering I, II and III (hard as hell) but since I haven't focused on those theories and practices anymore, I've lost my touch.

It's definitely not easy for a novice programmer to transition between paradigms..

How is platonism still so prevalent among mathematicians?

We know by now that there are different mathematical models depending on different axioms, like the axiom of choice. You can include or omit it from the model and you get consistent and useful but different mathematics in either case.
And there are other examples.

How does this not make it obvious that formalism, rather than platonism, is true?