Discrete math topics seems to be a US thing. While that is the system we are used to, many other countries don't focus on one math topic each year - they have a bit of each topic every year.

My kids did most of their elementary years in an immersion school that was based on a European school model. They did a wide variety of math topics each year, and they were clearly ahead of their public school peers when they switched to the local public school.

I think that there will still be discrete topics in middle/high school. The College Board wouldn't let the model change - too much money at stake with AP tests.