YouTube is only a medium. Other media include lectures (oral/visual), books, etc.
If you want to learn math on YouTube, you would need to find videos that convey the information you are trying to learn, in the format that makes it easy for you to understand.
There are many videos about math on YouTube. However (just like with any way of teaching, including books), there are good and bad ones. How can you decide which videos are the right ones for you? For example, Vi Hart has a lot of great videos about math, but I don’t think you would learn math from her videos.
If you want to learn basic math (through high school), I believe Khan Academy is a good place to start. After that, I would look at some university level courses such as Math and Logic Courses | Coursera, or MIT Free Online Course Materials.
p.s. Thinking about this further, I realized that Jo Boaler (Stanford University) has a great TED Talk on YouTube. Jo has some great ideas about learning math which you can review at her website: Inspiring Students to Math Success and a Growth Mindset