After 6 years I still don't understand this

Uhmm... no.

Math, like any science, is formulated through hypothesizing, experimenting and concluding. It's just less observation based like say astronomy. Theorems in math are tested theories and hold true for as long as until a new theory disproves it. In other sciences, theories are disproved by a newfound observation, which does happen every now and then. In math, theorems are logically proven so you do not see a theorem disproved very often (or at all) unless there is a logical fallacy. And like science, new theories and concept such as calculus and the imaginary number revolutionize and advance the field.

Division by zero isn't because people "agreed it's impossible". It is possible. It's just that it yields a logical error (1 = 0 or 1 = 2). 1 + 1 = 2 isn't because people agree. There is a theorem that proves that 1 + 1 = 2 is in fact true and it doesn't involve counting fingers and a bunch of scientists nodding their heads in agreement.

" "

Math = number of rules agreed by scientists all over the world with hypothesizing how logic should be written down.

It's only rules, not truth. That's why they invented 0 and infinity, just to keep the logic going.

That dividing by zero leads to a logical arrow, is the result of the rules of logic.