Math always seemed a bit arbitrary to me. Why and how did all those fields and branches develop, why are some so much more intuitive than others etc. What helped me cope with that challenge (and ultimately be a better learner / user of mathematics) was digging into the history of mathematics. Many great books in that genre but a very influential one for me was the Concise History of Mathematics by Dirk Jan Struik
That's because math is fundamentally arbitrary. This realization came to me late in life. Math was always presented as some aspect objective reality. However over time I've come to understand it as software for human brain. Using this math or that to describe something is often simply a matter of taste! Very similar to programming, in fact. Your study of history gives context to the question of utility different maths "packages" for certain problems, but does not invalidate your original impression.
I think "arbitrary" gives the wrong flavor here. Math is fundamentally curated.
It's easy to create something new, because you get to play with the rules - but unless it is in some sense deep, effective, and usually elegant [1] it won't stick around.
